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UNIVERSITY    OF     ILLINOIS     LIBRARY    AT    URBANA-CHAMPAIGN 


NIVERSITY  OF  ILLINOIS  BULLETIN 

Vol.  VII.  MARCH  7,  1910.  No.  27 

[Entered  February  14,  1902,  at  Urbana,  Illinois,  as  second-class  matter  under 
Act  of  Congress  of  July  16,  1894.  ] 


BULLETIN  No.   12 
DEPARTMENT  OF  CERAMICS 

A.   V.   BLEININGER,  Director 

NOTES  ON  THE  MANUFACTURE  OF 
ENAMEL  BRICK  WITH    SOME   INVESTIGA- 
TIONS ON  ENAMEL  BRICK  SLIPS 


BY 


R.  T.  STULL,   Urbana,  III. 


1909-1910 


PUBLISHED  FORTNIGHTLY  BY  THE  UNIVERSITY 


[Rei-rinted  from  Transactions  or  American  Ceramic  Society,  Vol.  XII. 
Paper  read  at  Pittsburgh  Meeting,  Febiuary,  1910] 


NOTES    ON    THE    MANUFACTURE    OF    ENAMEL 

BRICK  WITH  SOME  INVESTIGATIONS  ON 

ENAMEL  BRICK  SLIPS. 

BY 

K.  T.  Stull,  Urbana,  111. 

Aside  from  the  contribution  by  Barringer  in  Volume 
V  of  our  Transactions,  very  little  literature  can  be  found 
of  material  assistance  to  the  prospective  manufacturer  of 
enamel  brick. 

Although  the  fundamental  principles  of  ceramics 
apply  to  the  manufacture  of  enamel  brick,  they  have  not 
been  clearly  pointed  out  in  this  line  of  business;  besides, 
there  are  problems  peculiar  to  the  trade  which  need  more 
thorough  investigation. 

The  majority  of  men  in  America,  who  are  in  charge  of 
the  manufacturing  end,  are  of  foreign  birth.  They  have 
brought  their  experiences  and  recipes  with  them,  and 
have  gone  through  the  painful  experiences  of  applying 
them  to  our  conditions.  This  has  been  largely  responsible 
for  the  prevailing  belief  that  "we  must  go  abroad  to  get 
clays  for  our  slips.""  If  all  Pkirope  should  pass  stringent 
laws  prohibiting  the  exportation  of  her  clays,  it  is  not 
probable  that  the  American  white  ware  potters  and 
enamel  brick  makers  would  go  out  of  business,  nor  make 
anjr  great  sacrifices  in  the  quality  of  their  products. 

Clays  suitable  for  enamel  brick  bodies  should  possess 
low  shrinkages,  good  bond,  be  free  from  warping  and 
cracking,  stand  up  well  at  cone  4  or  higher,  and  burn  to  a 
light  color  comparatively  free  from  iron  spots. 

The  plastic  fireclays  are  well  suited  to  this  purpose. 
It  is  quite  essential,  however,  to  reduce  their  shrinkages 
by  the  addition  of  flint  clay  or  grog.  The  majority  of  body 
mixes  vary  from  GO  to  80  plastic  and  -10  to  20  non-plastic 

*  Instead  of  "engxjbe"   the  writer  prefers  to  use  the  word   "slip"  because 
it   is  the  term  universally  understood  by  enamel  brick  makers. 

3 


4  ON    THE    MANUFACTURE   OF   ENAMEL   BRICK. 

parts.  Some  clays  will  carry  a  small  percent  of  sand 
without  material  injury.  Oue  mixture  which  has  been  in 
use  for  several  years  is  composed  of  70  parts  plastic  clay, 
20  parts  grog,  and  10  parts  crushed  sand  stone. 

METHODS  OF  MANUFACTURE. 

In  general,  two  different  processes  of  manufacture  are 
recognized,  viz.,  one  fire  and  two  fire.  In  both  one  and 
two  fire  ware,  the  methods  of  applying  the  veneer  are 
practically  the  same,  the  distinguishing  feature  being 
that,  in  the  two  fire  process,  the  brick  are  first  biscuited 
at  a  low  temperature  before  the  veneer  is  applied.  Quite 
recently  mechanical  appliances  have  been  introduced 
which  promise  to  make  some  radical  changes  in  the  manu- 
facture of  enamel  brick.  For  the  present  work,  the  meth- 
ods of  manufacture  will  be  divided  into  two  general 
groups,  according  to  the  methods  of  application  of  the 
veneer. 

I.     Hand  Dipping  Process. 

(a)  Single  Fire: 

1.  Dipping  Stiff  Mud  Brick, 

2.  Dipping  Leather  Hard  Brick, 

3.  Dipping  Bone  Dry  Brick. 

(b)  Two  Fire:" 

1.     Dipping  Biscuited  Brick. 
II.     Mechanical  Veneering  Process. 
(a)      Single  Fire: 

1.     Veneering  Stiff  Mud  Column  and  Wire 
Cutting. 

A  favorite  method  of  making  enamel  brick  in  Europe 
is  by  dipping  a  stiff-mud  wire-cut  brick.  The  face  of  a 
iirst  quality  enamel  brick  must  be  as  near  perfect  as  it  is 
possible  to  make  it.  Since  the  brick  are  not  repressed, 
the  die  is  watched  with  the  greatest  care,  and  frequently 
lined  up  to  normal  size  in  order  to  take  up  the  wear. 

It  is  important  that  the  brick  be  cut  straight.  A 
method  in  vogue  is  to  cut  the  column  into  blocks  which 


ON    THE   MANUFACTURE   OF   ENAMEL   BRICK.  5 

are  dipped,  and  after  the  slip  has  hardened  sufficiently,  the 
blocks  are  "squared"  on  a  hand  cutting  table.  This  is 
also  an  effective  way  of  removing  the  excess  slip  on  the 
sides. 

Although  this  method  has  not  been  exploited  to  any 
extent  in  America,  it  has  many  advantages  well  worth 
investigating :  1.  Repressing  and  consequent  flaking  of 
the  slip  due  to  oil  on  the  surface  are  avoided.  2.  There 
is  a  better  bond  between  slip  and  body  since  the  two 
shrink  together  in  drying.  3.  The  necessity  of  storing 
the  brick  until  they  reach  leather  hard  consistency  is  eli- 
minated. 

In  the  leather  hard  method,  the  brick  are  allowed  to 
harden  by  partial  drying  until  nearly  all  drying  shrinkage 
has  ceased  before  they  are  dipped.  The  brick  may  be 
formed  on  a  soft-mud  machine,  or  "slush''  molded  by  hand 
in  wooden  molds,  hardened  down  to  a  stiff -mud  consistency 
and  re-pressed,  or,  more  commonly,  made  stiff  mud  on  a 
plunger  or  auger  machine,  wire  cut,  and  re-pressed.  Owing 
to  the  variation  in  size  and  shape,  the  soft-mud  machine 
method  is  to  be  recommended  only  where  two  grades  of 
brick  are  to  be  made.  By  sorting  the  brick  as  they  come 
from  the  repress,  those  which  are  true  in  form  and  size 
can  be  used  for  enameling  and  the  remainder  burned  for 
builders. 

The  process  of  slush  molding  and  repressing  by  hand 
is  very  similar  to  that  for  hand  made  fire  brick,  except 
that  more  care  is  taken  in  filling  and  dumping  the  molds 
and  greater  care  exercised  in  repressing. 

The  advantages  in  repressing  are  that  the  brick  can 
be  "squared  up,"  panelled  and  the  firm's  name  stamped 
on  the  side.  With  the  stiff-mud  brick  not  subjected  to 
the  repress,  the  brick  can  be  judiciously  cored  and  the 
lettering  stamped  on  the  back  side  of  the  column  by  a 
roller. 

A  few  plants  are  glazing  bone  dry  brick.  Although 
sold   as  enamel  brick  in  some  cases,  they  are  in  reality 


6  ON   THE   MANUFACTURE   OF   ENAMEL   BRICK. 

nothing  more  than  glazed  brick,  and  should  be  classed  as 
such. 

To  the  writer's  knowledge,  there  is  not  a  plant  at  the 
present  time  successfully  making  a  white  enamel  brick 
by  dipping  a  bone  dry  body  in  slip  and  glaze.  It  is  doubt- 
ful whether  this  method  will  ever  be  a  success  owing  to 
difficulties  encountered  in  cracking  ami  flaking  of  the  slip. 

In  the  two  fire  process  the  brick  may  be  made  soft- 
mud  repress,  stiff-mud  wire-cut,  stiff-mud  repress  or  dry- 
press  process.  The  brick  are  first  biscuited  at  heats  rang- 
ing from  cone  OS  to  cone  01,  then  dipped  in  slip  and  glaze 
and  given  the  glost  fire  at  cones  3  to  9.  A  few  plants  mak- 
ing dry  pressed  front  brick  from  fire  clays  are  enamelling 
their  culls,  which  are  too  soft  for  the  market  or  off  in 
color  but  otherwise  having  true  faces. 

Methods  of  Dipping-. 

In  some  cases  the  brick  are  given  one  dip  in  the  slip 
and  one  in  the  glaze,  but  in  most  cases  the  brick  are  given 
two  dips  in  the  slip  and  one  in  the  glaze.  A  factory  which 
has  been  brought  to  the  writer's  notice  sprays  on  the  first 
coat  and  dips  the  second  one.  Two  slips  of  different  com- 
position are  sometimes  employed,  the  first  dip  being  made 
in  a  slip  comparatively  high  in  ball  clay  and  correspond- 
ingly low  in  China  clay  or  kaolin.  Over  this  a  second  coat 
is  applied  composed  of  materials  giving  a  much  whiter 
surface. 

The  thickness  of  the  slip  is  an  important  factor.  It 
is  essential  that  it  be  applied  thick  enough  in  order  to 
form  a  smooth  coating  and  to  hide  the  character  of  the 
body  underneath.  In  the  two  fire  process  the  brick  may 
be  porous  enough  to  take  on  a  sufficient  coating  in  one 
dip,  but  for  stiff-mud  and  leather-hard  bodies,  one  dip  is 
seldom  sufficient,  except  in  cases  where  a  more  or  less 
opaque  glaze  is  applied  over.  The  proper  thickness  of  the 
slip  under  ordinary  conditions  is  from  three-hundredths 
to  five-hundredths  of  an  inch.     Where  the  slip  is  thin,  the 


ON   THE   MANUFACTURE   OF   ENAMEL   BRICK.  7 

differences  in  shrinkage  and  expansion  of  body  and  slip 
are  balanced  by  the  elasticity  of  the  slip,  thus  preventing 
rupture.  If  the  coating  of  slip  is  too  thick,  its  shrinkage 
and  expansive  forces  may  cause  cracking,  crazing  or 
flaking. 

The  glaze  applied  over  the  slip  should  be  quite  viscous 
so  as  to  prevent  excessive  flow  and  beading  along  the 
edges,  and  to  overcome  the  absorption  of  the  glaze  by  the 
slip  and  the  consequent  vitrifying  of  the  slip  which  would 
cause  the  dark  color  of  the  body  to  show  through. 

Defects  Appearing  After  Dipping. 

The  principal  defects  which  appear  after  dipping  be- 
fore the  brick  enter  the  kiln  are: 

1.  Pinholes. 

2.  Flaking. 

3.  Cracking. 

J'inholcs. 

Pinholes  may  occur  from  four  causes:  1.  Using  a 
freshly  made  slip.  2.  Pinholes  or  cavities  in  the  surface 
of  the  brick.  3.  Dust  on  the  face  to  be  dipped.  4.  Bad 
dipping. 

The  writer  has  seen  pinholes  appear  repeatedly  by 
dipping  brick  in  a  freshly  made  slip.  After  ageing  the 
slip  for  a  short  time,  pinholes  from  this  cause  disappeared. 
A  week's  ageing  of  the  slip  is  usually  sufficient. 

After  dipping,  the  pinholes  do  not  appear  until  the 
"water  gloss"  of  the  surface  begins  to  disappear.  Bubbles 
which  appear  on  the  surface  break,  leaving  small  cavities 
in  the  surface. 

2.  Air  is  entrapped  in  small  cavities  or  pores  in  the 
dipped  surface.  As  the  water  in  the  slip  is  absorbed  by 
the  brick,  the  air  in  these  small  cavities  is  forced  out, 
passing  up  through  the  slip,  thus  causing  pinholes. 

3.  In  dipping  a  dusty  surface,  air  is  entrapped  in 
films  around  the  dust  particles  and  in  cavities  between 


g  ON   THE   MANUFACTURE  OF   ENAMEL   BRICK. 

them.  As  the  water  in  the  slip  slowly  creeps  over  the 
surface  of  these  particles,  the  air  is  released  and  rises  to 
the  surface. 

In  order  to  overcome  pinholes  caused  by  dust  or 
minute  cavities  in  the  surface,  brick  makers  resort  to 
"scrubbing;"  i.  e.,  the  surfaces  to  be  eDameled  are  brushed 
over  with  a  stiff  brush  dipped  in  water,  or  more  commonly, 
in  a  slip  diluted  with  water.  Other  recipes  which  have 
been  in  use  are :  water,  slip  and  glue ;  water,  slip  and 
molasses;  water,  fire  clay  and  white  slip. 

4.  Air  may  be  entrapped  by  bad  dipping.  This  oc- 
curs if  a  flat  surface  of  the  brick  meets  the  surface  of  the 
slip  when  first  immersed. 

A  good  method  of  dipping  is  to  hold  the  back  of  the 
Itrick  in  the  palm  of  the  hand  with  face  to  be  dipped,  down. 
By  allowing  one  edge  of  the  brick  to  first  meet  the  surface 
of  the  slip  as  in  position  1,  the  slip  is  washed  across  the 
face  by  a  rocking  motion  through  2  to  3.  Then  by  the 
reverse  motion  (without  removing  the  brick  from  the  slip), 
the  brick  is  passed  back  through  4  to  5.  The  end  of  the 
brick  farthest  from  the  operator  is  then  raised  as  in  posi- 
tion 6,  which  allows  the  excess  slip  to  run  down  the  edge 
and  leave  at  the  corner  as  it  is  raised  from  the  slip.  The 
brick  is  then  quickly  inverted  and  slid  onto  a  bench. 

The  clipping  should  be  done  by  an  easy  swinging  mo- 
tion to  and  fro  without  a  halt  in  the  operation.  The  time 
required  for  a  single  dip  is  from  three  to  six  seconds,  and 
a  careful  dipper  can  perform  the  operation  alternately 
right  and  left  handed,  getting  very  little  slip  over  the 
edges. 


ON    THE   MANUFACTURE   OF   ENAMEL    BRICK. 


"RAINS'.    ArV.CE-R.   SOC.  VOL.  XII. 


/ 
\ 


Z  <- 


DiHererrt  Positior\s05  BricMn  Dipping- 


Flaking. 

Flaking  or  shelling  of  the  slip  is  due  to  lack  of  bond. 
It  may  occur  soon  after  dipping  or  may  not  appear  until 
the  brick  are  subjected  to  the  fire.  Lack  of  bond  may  be 
caused  by  oil  or  dust  on  the  surface,  or  by  unequal  shrink- 
age of  slip  and  body.  It  is  most  frequently  caused  by  too 
low  shrinkage  of  the  slip,  but  in  some  cases  it  is  caused 
by  too  high  shrinkage  of  the  slip.  In  the  latter  case  crack- 
ing and  flaking  will  appear  on  the  same  surface. 

Scrubbing  the  surface  before  clipping  not  only  pre- 
vents pinholes,  but  also  assists  adhesion  by  removing  dust 
and  oil  which  may  cause  an  otherwise  good  slip  to  flake. 

Slips  too  low  in  plastic  clay,  or  slips  too  high  in  kaolin 
or  China  clay  which  are  short  or  weak  in  character  will 
cause  flaking.  Where  flaking  is  due  to  low  shrinkage,  the 
remedy  is  to  increase  the  percent  of  plastic  clay  and  de- 


10  ON    THE    MANUFACTURE   OF   ENAMEL   BRICK. 

crease  the  non-plastic  portion.  Where  cracking'  and  flak- 
ing occur,  reduce  the  percent  of  clay  and  substitute  part 
ball  clay  for  China  clay  or  kaolin. 

The  tendencies  of  ball  clay  are  to  increase  shrinkage, 
impart  greater  adhesive  power  and  render  the  slip  more 
yielding  or  ductile  by  which  it  adjusts  itself  better  to  the 
brick,  thus  preventing  rupture. 

Some  English  recipes  for  slips  require  plaster  of  paris 
to  overcome  flaking.  It  is  necessary  in  such  cases  to  exer- 
cise care  in  burning,  besides,  the  cause  of  rough,  blistered 
and  scummed  glazes  can  frequently  be  traced  to  plaster  in 
the  slip.  The  use  of  plaster  to  prevent  flaking  is  unneces- 
sary, since  good  reliable  slips  can  be  had  without  it. 

Cracking. 

Cracking  may  be  caused  by:  1.  Excessive  shrinkage 
of  the  slip.  2.  Too  thick  a  coating  of  slip.  3.  Too  fine 
grinding  of  slip.  4.  In  dipping  leather  hard,  allowing  the 
brick  to  become  too  dry  before  dipping.  5.  Using  clays 
which  are  weak  or  have  low  tensile  strength. 

Cracking  may  be  overcome  by  substituting  a  clay  of 
low  shrinkage  for  one  of  higher ;  or  increasing  the  non- 
plastic  portion  and  decreasing  the  plastic  part,  such  as 
increasing  flint  and  feldspar  or  Cornwall  stone,  or  replac- 
ing part  raw  clay  with  calcined  clay. 

Blunging  the  slip  instead  of  grinding  is  to  be  recom- 
mended. The  use  of  a  small  quantity  of  carbonate  of  soda 
or  borax  is  found  to  be  beneficial  to  overcome  cracking. 
The  proper  amounts  of  these  soluble  materials  to  use  is  an 
important  factor  and  varies  in  different  slips,  hence  the 
amount  should  be  determined  experimentally.  Slips  high 
in  clay  require  more  than  slips  low  in  clay. 

Mechanical  Methods  of  Applying  Slip. 

The  most  universal  method  of  applying  slip  and  glaze 
is  by  hand  dipping  and  removing  the  surplus  on  the  sides 
by  scraping  with  a  knife  or  scratching  with  a  fine  wire 
brush.     Quite  recently  a  leading  enamel  brick  plant  has 


ON    THE    MANUFACTURE   OF   ENAMEL   BRICK.  11 

been  experimenting  with  a  dipping  machine  similar  in 
construction  to  that  used  for  dipping  wall  tile.  The  ma- 
chine is  made  somewhat  larger,  with  a  few  minor  changes 
in  its  construction  in  order  to  make  it  more  suitable  for 
its  new  purpose. 

The  automatic  veneering  process  is  one  which  has  a 
great  future.  The  process  consists  in  veneering  a  column 
of  stiff  mud  clav  after  it  issues  from  a  die.  For  this  pur- 
pose a  veneering  device  is  attached  to  the  end  of  the  die 
or  placed  in  front  of  it  for  spreading  the  slip  in  a  layer 
about  one-sixteenth  of  an  inch  thick  upon  the  faces  to  be 
veneered. 

Although  there  are  four  American  patents  on  devices 
for  veneering  a  column  of  clav,  but  one  of  these  seems  to 
be  successful  for  the  manufacture  of  enameled  brick,  viz., 
the  Ramsay  patent,  which  has  recently  been  brought  to 
public  notice  by  an  infringement  suit. 

The  veneering  device  consists  of  two  rectangular 
frames  A  and  B,  called  slickers,  having  two  plates  between 
as  C,  one  at  each  side.  These  slickers  are  fastened  to- 
gether by  two  bolts  at  each  side  as  DD.  The  apparatus 
is  supported  by  the  die  and  about  one  inch  in  front  of  it 
on  two  rods  E,  one  at  each  side.  Figs.  2  and  3  represent 
the  apparatus  rigged  for  making  stretchers,  in  which  case 
the  top  of  the  column  is  veneered.  Fig.  4,  a  vertical  sec- 
tion across  the  column,  shows  the  arrangement  for  making 
quoins,  in  which  case  the  top  and  one  side  of  the  column 
are  veneered.  The  same  principle  is  used  for  making  bull 
nose  and  other  shapes. 

"A"  is  the  surface  preparing  slicker  having  the  same 
inside  dimensions  as  the  delivery  end  of  the  die.  "B''  is 
the  slip  slicker  and  is  five  sixty-fourths  of  an  inch  larger 
than  the  surface  preparing  slicker  at  all  points  where  the 
slip  is  to  be  applied  to  the  column.  "S,"  the  slip  which  is 
pugged  to  about  the  same  consistency  as  clay  userl  for 
pressing  white  ware,  is  placed  upon  the  column  between 
A  and  B.    As  the  column  moves  forward  the  slip  adheres 


12 


ON    THE   MANUFACTURE   OF   ENAMEL    BRICK. 


TRANS.  AM  CE  f?.  S>OC.  VOLXII. 


5TULL. 


SVdeM\evt  S\\ov*'vftc^tiAe\V\o4 
OS  Meneev'wx^To?  Q*  Co\un\n. 


<L_ 


Fiq.3  """  c^ 

Sec\\ov\,S'\AeM'\e>N. 


A— P. 


?^A 


End\T\e>w  SV\ow'm^N\e\Y\od  OS 
-   \jeneer'm^Topi\t\dS\Ae05Co\vAmi\. 


OX    THE   MANUFACTURE   OF   ENAMEL   BRICK.  13 

to  it  and  rolls  over  and  over,  unwinding  as  it  were,  and  is 
spread  in  a  coating  about  one-sixteenth  of  an  inch  in 
thickness  by  the  slip  slicker  "B." 

The  column  is  cut  into  brick  on  a  hand  cutting  table 
of  special  design  and  dried  on  a  hot  floor.  The  bricks  are 
loaded  on  trucks  and  the  glaze  applied  by  a  large  sprayer 
having  the  air  and  glaze  under  a  pressure  of  forty  to  sixty 
pounds.     The  brick  are  then  set  and  burned  single  fire. 

Setting. 

Of  the  three  methods  of  burning,  viz.,  open  fire,  burn- 
ing in  muffles  and  burning  in  saggers,  the  open  fire  method 
is  most  economical  but  requires  considerable  care  and  skill 
in  setting.  Some  brick  makers  set  the  brick  in  piers,  but 
the  writer  prefers  setting  in  benches  extending  across  the 
kiln.  In  two  fire  ware  the  brick  may  be  set  on  the  flat  as 
described  by  Barringer,1  but  for  single  fire  ware  this 
method  causes  considerable  loss  in  cracking  owing  to 
shrinkage.  In  order  to  overcome  this  difficulty,  the 
stretchers  on  the  outside  of  the  benches  are  set  on  end  and 
shapes  set  flat  in  the  middle  in  piers,  (Fig.  5). 

In  the  single  fire  method  the  brick  should  go  into  the 
kiln  bone  dry.  In  the  writer's  experience,  brick  which 
Avere  set  wet  frequently  came  out  with  a  dry,  rough  sur- 
face as  though  the  glaze  were  underfired.  At  other  times 
the  glaze  would  be  blistered  or  badly  scummed.  These 
brick  were  called  by  the  workmen  "steamed  brick."  Re- 
peated burning  of  these  brick  made  no  appreciable  differ- 
ence in  their  appearance. 

It  is  probable  that  these  brick  being  wet,  took  up 
sulphur  dioxide  from  the  kiln  gases,  which  in  turn  oxi- 
dized to  sulphuric  acid.  This  naturally  would  combine 
with  lime  and  zinc  oxide  present  in  the  glaze,  and  since 
the  kilns  were  burned  oxidizing  throughout,  the  sulphates 
would  naturallv  remain  as  such. 


1  Trans.   A.   C.    S.,   Vol.   V,   p.   273. 


14 


ON    THE    MANUFACTURE    OF   ENAMEL    EHICK. 


TRANS.  AM    CER.SOC.  VOLXII. 


PotWcm  o?r  BencK}C^uo\n5  matV\eNUdd\e, 
Stve\cV\ers  QoAs\de. 


INVESTIGATIONS  BY  THE  WRITER. 
(Ceramic  Laboratory,  University  of  Illinois) 

The  following"  work  comprises  sonic  investigations  on 
enamel  brick  slips  applied  to  leather  hard,  bone  dry  and 
biscuit  bodies  between  the  limits 

25  to  75  parts  clay  materials, 

75  to  25  parts  non-plastic  materials. 
The  ceramic  materials  employed  were: 

Georgia  kaolin, 

North  Carolina  kaolir, 

Tennessee  ball  clay  (No.  1), 

Brandy  wine  feldspar, 

Ohio  flint  (8  hr.  grind), 

M.  G.  R.  English  China  clay, 


ON   THE   MANUFACTURE   OF   ENAMEL   BRICK.  15 

Pikes  English  ball  clay  (No.  20), 
English  Cornwall  stone, 
Carbonate  of  soda. 

The  objects  of  the  work  were  to  determine  the  range 
of  good  slips  within  the  above  named  limits,  to  study  the 
causes  and  remedies  of  defects,  and  to  compare  the  slip 
making  values  of  some  of  the  English  materials  with  those 
of  a  few  American  materials. 

If  a  brick  is  to  come  from  the  kiln  as  a  No.  1  article, 
it  must  first  enter  the  kiln  in  No.  1  condition.  The  first 
step  undertaken  in  the  work  was,  to  determine  the  ratios 
of  plastic  to  non-plastic  portions  for  slips  which  would  fit 
the  bodies  perfectly  in  dipping,  and  which  were  to  be  used 
as  bases  for  making  the  slips  for  the  burning  trials.  For 
this  purpose  series  27,  28,  20  and  30  were  constructed. 

Carbonate  of  soda  was  kept  constant  at  one  percent 
in  all  slips  throughout  the  work.  All  slips  contained  ten 
percent  of  ball  clay,  two  different  ball  clays  being  em- 
ployed for  comparison. 

The  slips  were  weighed  dry,  blunged,  passed  through 
a  100  mesh  screen,  set  at  1500  to  1520  B  &  L  hydrometer, 
and  placed  in  sealed  jars  and  allowed  to  age  for  one  week. 

The  body  for  the  briquettes  was  composed  of  TO  parts 
plastic  fire  clay  and  30  parts  16  mesh  grog.  The  trials 
were  made  stiff  mud  on  a  small  auger  machine  and  wire 
cut. 

The  trials  received  two  dips  in  the  slip,  the  dipped 
surface  first  being  scrubbed  with  two  parts  water  and  one 
part  of  the  slip  to  be  applied. 


it; 


ON    THE   MANUFACTURE   OF   ENAMEL    BRICK. 


SERIES   27. 
Ga.  Kaolin— No.  1  Tenn.  Ball. 


No. 

Kaolin 

Tenn. 
No.  1 
Ball. 

Flint 

Car- 
bonate 
of  Soda 

On 

Leather 
Hird 

On 

Bone 
Dry 

On  Biscuit 

Basis 

for 

Series 

185 
186 

15 

25 
35 

45 
55 
65 

10 

10 
10 

10 

10 
10 

75 

65 

55 

45 
35 
25 

1 

1 

1 

1 
1 
1 

Flaked 
Flaked 

Flaked 

Cracked 

Cracked 

Cracked 

Cracked 

Flaked 
Flaked 
Cracked 
Cracked 

Cracked 
Cracked 
Cracked 

Good 

Cracked 

Cracked 

Flaked 

Cracked 

Cracked 

Cracked 

31  and  50 

187 

188 
189 

190 

In  series  27  all  slips  flaked  on  leather  hard  trials,  and 
flaked  and  cracked  on  bone  dry.  Slip  No.  185,  containing 
15  Georgia  kaolin  and  75  flint,  was  good  on  biscuit.  This 
slip  was  selected  as  the  basis  for  Series  31  and  50.  All 
other  slips  cracked  and  flaked. 

SERIES   28. 
N.   C.  Kaolin— No.  1   Tenn.  Ball. 


'   N.  C. 
Kaolin 

Tenn. 

Car- 

on 

On 

No. 

No.  1 

Flint 

bonate 

Leather 

Bone 

On  Biscuit 

Basis  for  Series 

Ball 

of  Soda 

Hard 

Dry 

191 

15 

10 

75 

1 

Flaked 

Flaked 

Good 

32    and    51 

192 

25 

10 

65 

1 

Flaked 

Flaked 

Good 

33   and   52 

193 

35 

10 

55 

1 

Flaked 

Flaked 

Good 

34    and    53 

194 

45 

10 

45 

1 

Flaked 

Flaked 

Good 

35    and    54 

195 

55 

10 

35 

1 

Flaked 

Flaked 

Good 

36    and    55 

196 

65 

10 

25 

1 

Flaked 

! 

Flaked 

Good 

37    and   56 

! 

In  Series  28  all  slips  fit  perfectly  on  biscuit  but  flaked 
on  bone  dry  and  leather  hard  bodies. 

SERIES   29. 
N.  C.  Kaolin— English  Ball. 


No. 

N.    C. 
Kaolin 

English 
Ball 

Flint 

Carbon- 

nate 
r.f  Soda. 

On 

Leather 

Hard 

On 
Bone 
Dry 

On  Biscuit 

Basis  for  Series 

197 

15 

10 

75 

1 

Flaked 

Good 

Good 

38  and  57 

198 

25 

10 

65 

1 

Flaked 

Good 

Good 

39  and  58 

199 

35 

10 

55 

1 

Flaked 

Good 

Good 

40  and  59 

200 

45 

10 

45 

1 

Flaked 

Doubtful 

Good 

41  and  60 

201 

55 

10 

35 

1 

Good 

Cracked 

Good 

42  and  61 

202 

65 

10 

25 

1 

Good 

Cracked 

Good 

43  and  62 

ON   THE   MANUFACTURE   OP   ENAMEL  BRICK. 


17 


Series  29  is  the  same  as  Series  28  except  that  Pikes 
No.  20  English  ball  clay  replaces  Tennessee  ball.  In  this 
series  all  slips  work  perfectly  on  biscuit,  the  three  lowest 
in  clay  fit  bone  dry,  the  others  cracked.  The  two  highest 
in  clay  fit  perfectly  on  leather  hard. 

SERIES  30. 
English  China — English  Ball. 


No. 

Knglish 

Cm  na 

English 
Ball 

Flint 

Carbon- 
ate of 
Soda 

On 
Leather 
Hard 

On  Bone  Dry 

On    Biscuit 

Basis  for  Series 

203 

15 

10 

75 

1 

Flaked 

Good 

Good 

44  and  63 

204 

25 

10 

65 

1 

Good 

Good 

Good 

45  and  64 

205 

35 

10 

55 

1 

Good 

Cracked 

Cracked 

46  and  65 

206 

45 

10 

45 

1 

Good 

Cracked 

Cracked 

47  and  66 

207 

55 

10 

35 

1 

Good 

Cracked 

Cracked 

48  and  67 

208 

65 

10 

25 

1 

Good 

Cracked 

Cracked 

49  and  68 

Slips  containing  15  to  25  China  clay  were  good  on 
biseuil  and  bone  dry,  the  remainder  cracked.  The  slip 
lowest  in  clay  flaked  on  leather  hard,  the  remainder  were 
good. 

Limits  of  Plastic  and  Non-Plastic  for  Dipping. 

Selecting  all  slips  which  are  good  in  the  above  four 
series,  we  find  that  for  leather  hard,  perfect  fitting  slips 
in  dipping  lie  within  the  range: 

Clay     35  to  75 

Non-plastic    65  to  25 

For  dipping  bone  dry: — 

Clay     25  to  45 

Non-plastic    75  to  55 

For  dipping  biscuit: — 

Clay     25  to  75 

Non-plastic    75  to  25 

Undoubtedly  slips  higher  in  clay  would  dip  well  on 
leather  hard  trials,  but  these  were  considered  as  imprac- 
tical on  account  of  crazing  after  burning,  as  will  be  shown 
later  on. 


18  ON   THE   MANUFACTURE   OF   ENAMEL    BRICK. 

Slips  lower  in  clay  would  probably  clip  perfectly  on 
biscuit,  and  here  again  we  find  crazing. 

After  determining  the  limits  of  plastic  and  non- 
plastic  portions  for  perfect  fitting  slips  in  dipping,  the  next 
step  in  the  work  was  to  select  each  of  the  perfect  working- 
slips  as  a  basis  of  a  series  in  which  the  non-plastic  portion 
was  varied  between  flint  and  flux. 

Series  31  and  50  are  the  only  two  containing  Georgia 
kaolin  which  dipped  well  on  biscuit.  The  other  series  are 
arranged  in  six  groups,  the  flux  in  the  first  three  being 
feldspar.  The  other  three  groups  are  a  repetition  of  the 
first  three,  except  that  Cornwall  stone  was  used  as  the  flux 
in  place  of  the  feldspar. 

Three  different  burns  were  made,  viz.,  cones  4,  6  and 
8.  The  variation  in  the  kiln  was  such  as  to  give  cone  2  in 
the  coolest  part  of  the  cone  4  burn,  and  cone  9  in  the 
hottest  part  of  the  cone  8  burn.  Trials  were  set  on  edge 
in  tile  saggers.  Three  trials  of  each  slip  were  placed  in 
each  burn,  two  having  glaze  No.  51  applied  over  and  the 
third  slip  left  unglazed.  Cones  were  also  placed  in  each 
sagger. 

A  portion  of  each  slip  was  cast  ^4  x  y2  x  1%  inches  in 
plaster  molds.  These  cast  trials  Avere  placed  in  the  saggers 
with  the  dipped  trials  and  used  for  determining  the  poros- 
ity of  the  slips.  It  was  desirable  to  know  what  relation 
porosity  had  to  the  ability  of  slips  to  stand  the  freezing- 
test.  This  part  of  the  work  is  under  way  and  not  com- 
pleted at  the  present  writing. 


1  Trans.  A.  C.   S.,  Vol.  X,  p.   21S. 


ON   THE   MANUFACTURE   OF   ENAMEL   BRICK. 


19 


SERIES   31. 
(On  Biscuit) 


No. 

Constant 

Flint 

Spar 

Cone  5 

Cone  7 

Cone  9 

L-J   O   — 

209 

60 

15 

Crazed 

Crazed 

Crazed 

210 

•  y-i  -Q 

55 

20 

Crazed 

Crazed 

Crazed 

211 

:      o 

50 

25 

Crazed 

Crazed 

Crazed 

212 

:  £  «-i 

45 

30 

Crazed 

Crazed 

Crazed 

213 

o 

40 

35 

Crazed 

Crazed 

Crazed 

214 

£%2 

35 

40 

Crazed 

Crazed 

Crazed 

215 

Kao 
n.  B 
bona 

30 

40 

Crazed 

Crazed 

Crazed 

216 

25 

50 

Crazed 

Crazed 

Crazed 

.  s  - 
ci  v  d 

CrC 

All  are  good  smooth  slips  but  crazed.  The  glaze  tends 
to  decrease  crazing  of  the  slip.  Crazing  of  slip  increases 
with  increase  in  temperature.  Crazing  decreases  with  re- 
placement of  flint  by  feldspar.  No.  209  is  a  beautiful 
white,  the  whitest  slip  in  the  entire  work. 

Group  I — Series  32  to  37. 

SERIES  32. 
(On  Biscuit) 


217 
218 
219 
220 
221 
222 
223 
224 


•    33 
O 

Z  <t-i 


2  "3  o 

S   Co  ^ 
•   A    O 


60 

15 

55 

20 

50 

25 

45 

30 

40 

35 

35 

40 

30 

45 

25 

50 

Crazed 
Crazed 
Crazed 
Crazed 
Crazed 
Crazed 
Crazed 
Good 


Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

Slightly 

Crazed 


Crazed 
Crazed 
Crazed 
Crazed 
Crazed 
Crazed 
Crazed 
Good 


All  are  good  slips  except  for  crazing.     Crazing  de- 
creases from  217  to  224  due  to  replacement  of  flint  by 


20 


ON    THE   MANUFACTURE   OF   ENAMEL   BRICK. 


feldspar.  Crazing  of  slips  increase  with  increase  in  tem- 
perature. No.  224  is  highly  vitrified  at  Cone  9.  This  slip 
can  be  called  good  at  Coue  6,  but  is  too  translucent  at 
Cone  9.     Slips  are  slightly  cream  colored. 


SERIES  33. 
(On  Biscuit) 


No. 

Constant 

Flint 

Spar 

Cone  6 

Cone  7 

Cone  9 

1SOH 
!N  rH 

225 

50 

15 

Good 

Good 

Good 

226 

rH  >rj 

45 

20 

Good 

Good 

Good 

227 

O 

40 

25 

Good 

Good 

Good 

228 

35 

30 

Good 

Good 

Good 

229 

.So 

30 

35 

Good 

Good 

Good 

230 

2  ^  <f 

25 

40 

Good 

Good 

Good 

231 

N.   C.   K 
Tenn.  B 
Carbona 

20 

45 

Good 

Good 

Good 

232 

15 

50 

Good 

Good 

Good 

All  slips  work  perfectly.  The  10%  increase  in  clay 
in  this  series  above  that  in  Series  32  has  eliminated  craz- 
ing entirely.  Slips  229  to  232  are  translucent  at  cone  8. 
Slips  are  a  light  cream  in  color. 


SERIES   34. 
(On  Biscuit) 


No. 

Constant 

Flint 

Spar 

Cone  6 

Cone  7 

Cone  9 

Ifi  O  r-l 

233 

45 

10 

Good 

Good 

Good 

234 

■rH  rs 

40 

15 

Good 

Good 

Good 

235 

lin... 
I   No. 
of  So 

35 

20 

Good 

Good 

Good 

236 

30 

25 

Good 

Good 

Good 

237 

25 

30 

Good 

Good 

Good 

238 

2"S  ® 

20 

35 

Good 

Good 

Good 

239 

&m  £ 

15 

40 

Good 

Good 

Good 

240 

N.   C. 
Tenn. 
Carboi 

10 

45      I 

Good 

Good 

Good 

OX    THE    MANUFACTURE   OF   ENAMEL   BRICK. 


This  series  is  similar  to  Series  33.     Xo  bad  defects. 
Slips  237  to  240  are  vitrified  to  a  blue-white  at  Cone  9. 

SERIES  35. 
(On  Biscuit) 


No. 

Constant 

Flint 

Spar 

Cone  6 

Cone  7 

Cone  9 

lOOH 
■*  l-i 

241 

40 

5 

Good 

Good 

Good 

242 

tH    '72 

35 

10 

Good 

Good 

Good 

243 

C 
o't» 

30 

15 

Good 

Good 

Good 

244 

25 

20 

Good 

Good 

Good 

245 

•"      o 

20 

25 

Cracked 

Cracked 

Cracked 

246 

irt  v 

15 

30 

Cracked 

Cracked 

Cracked 

247 

N.  C.  K 
Tenn.  B 
Carbona 

10 

35 

Cracked 

Cracked 

Cracked 

Slips  arc  very  good  except  a  slight  tendency  to  crack. 
Cracking  increases  with  decrease  in  flint  and  increase  in 
feldspar.  Slips  245  to  247  are  translucent  at  Cone  9. 
Nearly  all  the  glazed  trials  are  good.  Glaze  tends  to  over- 
come cracking-  of  the  slip. 

SERIES   36. 
(On  Biscuit) 


Nt>. 

Constant 

Flint 

Spar 

Cone  6 

Cone  7 

Cone  9 

24s 

in 

©  iH 
rH 

H  ~ 

30 

5 

Good 

Good 

Good 

249 

O 

25 

10 

Good 

Good 

Good 

250 

£ 

20 

15 

Good 

Good 

Good 

251 

.=  '  '  o 

15 

20 

Cracked 

Cracked 

Cracked 

252 

§-3  2 

10 

25 

Cracked 

Cracked 

Cracked 

253 

N.  C.  K 
Tenn.  B 
Carbona 

5 

30 

Cracked 

Cracked 

Cracked 

This  series  is  similar  to  Series  35.    The  cracking,  how 
ever,  is  a  little  more  prominent. 


22 


ON   THE   MANUFACTURE   OF   ENAMEL   BRICK. 


SERIES   37. 
(On  Biscuit) 


Constant: 

N.   C.  Kaolin,  G5;   Tenn. 

Ball  No.  1,  10;  Carbonate  of  Soda,  1. 

No. 

Flint 

Spar 

Cone  3 

Cone  6              1             Cone  S 

Unglazed       1     Glazed 

Unglazed      I      Glazed     /    Unglazed      |        Glazed 

254 

20 

5 

Cracked 

Crazed 

Cracked 

Good 

Cracked 

Cracked 

255 

15 

10 

Cracked 

Crazed 

Cracked 

Good 

Cracked 

Good 

256 

10 

15 

Cracked 

Crazed 

Cracked 

Crazed 

Cracked 

Good 

257 

5 

20 

Cracked 

Crazed 

Cracked 

Crazed 

Cracked 

Good 

258 

0 

25 

Cracked 

Crazed 

Cracked 

Crazed 

Cracked 

Good 

All  slips  cracked.  Glaze  tends  to  prevent  cracking  of 
slip.  Slips  did  not  craze,  but  glazes  crazed  over  slips  in 
fine  zig-zag  lines.  Increasing  temperature  of  firing  de- 
creases crazing  of  the  glaze. 

The  six  different  groups  were  plotted  on  tri-axial  dia- 
grams. In  many  cases  the  unglazed  slips  were  defective 
and  the  same  slips  glazed  were  good.  Only  those  slips 
were  plotted  as  good  which  were  sound  both  glazed  and 
unglazed,  and  all  such  slips  that  were  sound  at  one  tem- 
perature, but  may  have  been  slightly  defective  at  some 
other  temperature,  were  plotted  as  good.  Slips  which  were 
translucent  (due  to  vitrification)  but  otherwise  perfect 
were  also  plotted  as  good. 


ON   THE   MANUFACTURE   OF  ENAMEL   BRICK. 


23 


TRANS.  AM.CER.  SOC.  VOL. XII. 

Group  I. 

NX.  Kaolin  -  15 to  65 
Brandywi7ie6/?cm5to50 
Oftio8ffr.nint~0tb60 

Cons  tants  Afot  Plotted  § 

TermBallNo./  ~/o 
Ca  r ton  ate  Soda& 
-/  ^ 


Clay 


A  ■  Good  On  Biscuit 
K  =  Craved  »      » 
C  =  CvacKed  »     » 


+  =  dli/is  That  O id  Not  Craze       0^  fr 
But  Over  Wnich  Glajecrajed.  cX" 


Conclusions  on  Group  I. 

Grazing  \  A  high  content  of  flint  evidently  causes 
crazing  of  the  slip.  Decreasing  flint  and  increasing  clay 
or  feldspar,  or  both,  decreases  crazing.  Increasing  clay  is 
more  effective  in  overcoming  crazing  than  increasing  feld- 
spar. With  flint  constant,  decreasing  clay  and  increasing 
feldspar,  increases  crazing.  Crazing  of  the  slip  increases 
with  increase  in  burning  temperature. 

A  high  content  of  clay  does  not  cause  the  slip  to  craze, 
but  causes  the  glaze  applied  over  the  slip  to  craze.  De- 
creasing clay  and  increasing  flint  or  feldspar,  or  both,  in 
the  slip  decreases  crazing  of  the  glaze.  Increasing  the 
burning  temperature  decreases  glaze  crazing. 

Cracking :  Excessive  clay  in  the  slip  causes  cracking 
during  burning.     Decreasing  clay  and  increasing  flint  or 


24 


ON   THE   MANUFACTURE   OF   ENAMEL   BRICK. 


feldspar,  or  both,  decreases  cracking.  Increasing  flint  de- 
creases cracking  more  effectively  than  increasing  feldspar. 
With  clay  constant,  decreasing  flint  and  increasing  feld- 
spar increases  cracking. 

Good  slips  in  this  group  on  a  biscuit  body  are  found 
between  the  limits : 

Georgia    Kaolin    15  to  55 

Flint     10  -to  50 

Feldspar     5  to  50 

Ball   Clay  10  J  Constant 

Carbonate  of  Soda   1  \ 

Group  II.    Series  38  to  43. 

SERIES  38. 
(On  Biscuit) 


Const 

mt: 

N.  C.  Kaolin,  15;  English  Ball 

,  10;  Carbonate  of  Soda.  1. 

1 

Cone   3 

Cone  G 

Cone  8 

No- 

Flint 

Spar 

Unglazed  l 

Glazed 

Unglaze.d 

Glazed 

Unglazed 

Glazed 

2:9 

GO 

15 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

2«0 

55 

20 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

Good 

261 

5(1 

2o 

Crazed 

Crazed 

Crazed 

Good 

Crazed 

Good 

26  -1 

45 

30 

Crazed 

Crazed 

Good 

Good 

Crazed 

Good 

263 

40 

35 

Good 

Good 

Good 

Good 

Crazed 

Good 

264 

35 

4d 

Good 

Good 

Good 

Good 

Crazed 

Good 

265 

HO 

4o 

Good 

Good 

Good 

Good 

Crazed 

Good 

266 

25 

50 

Good 

Good 

Good 

Good 

Crazed 

Good 

267 

20 

55 

Good 

Good 

Good 

Good 

Crazed 

Good 

Crazing  of  unglazed  slips  increases  and  crazing  of 
glazed  slips  decreases  with  increase  in  temperature.  Graz- 
ing decreases  with  increase  in  feldspar.  Aside  from  craz- 
ing, slips  fit  perfectly.  Slips  264  to  207  are  translucent  at 
Gone  6,  due  to  vitrification.  Slips  201  to  207  are  translu- 
cent at  Cone  9. 


ON   THE   MANUFACTURE   OF   ENAMEL   BRICK. 


25 


SERIES  38. 
(On  Bone  Dry) 


No, 

Cone  3 

Cone  5 

Com 

s 

Unglazed 

I      Glazed 

Unglazed 

I      Glazed 

Unglazed 

Glazed 

259 

Crazed 
Cracked 

Crazed 

Crazed 
Cracked 

Crazed 

Crazed 
Craeked 

Good 

260 

Crazed 
Cracked 

Crazed 

Crazed 
Cracked 

Good 

Crazed 
Cracked 

Good 

261 

Crazed 
Cracked 

Crazed 

Crazed 
Cracked 

Good 

Crazed 
Cracked 

Good 

262 

Crazed 
Cracked 

Good 

Crazed 
Cracked 

Good 

Cracked 

Good 

263 

Crazed 

Good 

Crazed 
Cracked 

Good 

Good   ? 

Good 

264 

Crazed 

Good 

Cracked 

Good 

Cracked 

Good 

265 

Good 

Good 

Cracked 

Good 

Good   ? 

Good 

266 

Good 

Good 

Good 

Good 

Good   ? 

Good 

267 

Good 

Good 

Good 

Good 

Cracked 

Good 

Slips  show  a  tendency  to  crack.  Cracking  does  not 
seem  to  be  influenced  by  variation  in  composition  or  heat 
treatment.  Cracks  extend  down  into  the  body  about  1/32 
to  1/16  of  an  inch. 

SERIES   39. 
(On  Biscuit) 


Const  Hit 

N. 

C  Kaolin,  25;  En 

glish  Ball, 

10;  Carbonate  of  So 

da,  1. 

Con 

e  4 

Cone  6 

Cone  3 

No 

Unglazed 

Glazed 

Unelazed     I       Glazed 

Unglazed    |         Glazed 

268 

50 

15 

Good 

Good 

Good 

Good 

Cracked 

Good 

269 

45 

20 

Good 

Good 

Good 

Good 

Cracked 

Good 

270 

40 

25 

Good 

Good 

Good 

Good 

Cracked 

Cracked 

271 

35 

30 

Good 

Good 

Good 

Good 

Good 

Good 

272 

30 

Rfi 

Good 

Good 

Good 

Good 

Good 

Good 

273 

25 

40' 

Good 

Good 

Cracked 

Cracked 

Cracked 

Cracked 

274 

20 

45 

Good 

Good 

Cracked 

Good 

Good 

Good 

275 

15 

50 

Good 

Good 

Cracked 

Good 

Good 

Good 

Slips  have  a  slight  tendency  to  crack,  which  increases 
with  increase  in  feldspar  and  temperature.  Glaze  over  the 
slip  tends  to  prevent  cracking.  (See  Pig.  6).  All  slips 
are  opaque  at  Cone  6.  Slips  272  to  275  are  vitrified  and 
translucent  at  Cone  8. 


26 


ON   THE   MANUFACTURE   OF   ENAMEL   BRICK. 


TRAN5.AM-CER.  SOC.  VOL. XII. 


5TULL 


ILLUSTRATIONS  OF  GLAZE  PREVENTING  SLIPS 
FROM    CRACKING. 


SERIES  39. 

(On  Bone  Dry) 

No. 

Cone  4 

Cone  6 

Cone  8 

Unelazed      |         Glazed 

Unclazed      I           Glazed 

Unglazrd       |         r:laze4 

268 

Cracked 

Good 

Cracked 

Cracked 

Cracked 

Cracked 

269 

Cracked 

Good 

Cracked 

Good 

Cracked 

Good 

270 

Cracked 

Cracked 

('racked 

Cracked 

Cracked 

Cracked 

271 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

272 

Cracked 

Cracked 

Cracked 

Good 

Cracked 

Cracked 

273 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

274 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

275 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracking  quite  bad;  worse  than  series  38. 


ON   THE   MANUFACTURE   OF  ENAMEL   BRICK. 
SERIES  40. 
(On  Biscuit) 


27 


Constant:     N.  C.  Kaolin,  35;  English  Ball,  10;  Carbonate  of  Soda,  1. 

No. 

Flint 

Cone  4 
Spar1 

1     Unglazed    1        Glazed 

Cone  6 

Cone  9 

Unelazed      I         Glazed 

Unglazed    I        Glazed 

276 

277 
278 
279 
280 
281 
282 
283 


45 

10 

Cracked 

Cracked 

40 

15 

Cracked 

Cracked 

85 

20 

Cracked 

Cracked 

30 

2."> 

Cracked 

Cracked 

2fi 

30 

Cracked 

Cracked 

20 

35 

Cracked 

Cracked 

15 

40 

Cracked 

Cracked 

10 

45 

Cracked 

Good 

Cracked 
Cracked 
Cracked 
Cracked 
Cracked 
Cracked 
Cracked 
Cracked 


Cracked 

Cracked ; 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Good 

Cracked 

Cracked 

Cracked 

Good 

Cracked 

Cracked 
Cracked 
Cracked 
Cracked 
Cracked 
Cracked 
Cracked 
Good 


Cracking  of  slips  very  bad.  Cracking  decreases  with 
increase  in  feldspar.  Glaze  tends  to  prevent  cracking  of 
the  slip.  All  slips  are  opaque  at  Cone  4.  Slips  281  to  283 
at  Cone  6,  and  279  to  283  at  Cone  9  are  vitrified. 


SERIES  40. 


(On  Bone  Dry) 


276 

Cracked 

Cracked 

Cracked 

277 

Cracked 

Cracked 

Cracked 

278 

Cracked 

Cracked 

Cracked 

279 

Cracked 

Cracked 

Cracked 

280 

Cracked 

Cracked 

Cracked 

281 

Cracked 

Cracked 

Cracked 

282 

Cracked 

Cracked 

Cracked 

283 

Cracked 

Cracked 

Cracked 

All  slips  both  glazed  and  unglazed  crack  badly.  Crack- 
ing extends  through  slips  into  the  body. 


28 


ON    THE   MANUFACTURE   OF   ENAMEL   BRICK. 

SERIES  41. 
(On  Biscuit) 


Constant:     N.   C.  Kaolin,   45;   English   Ball,   10;   Carbonate  of   Soda.   1. 

Flint 

Spar 

Cone  5 

Cone  7                                        Cone  9 

Unglazed    I         Glazed 

Unglazed      |        Glazed 

Unglazed      I         Glazed 

284 

35 

10 

Cracked 

Good 

Cracked 

Good 

Good 

Cracked 

285 

80 

15 

Good 

Good 

Cracked 

Good 

Good 

Good 

286 

25 

20 

Good 

Good 

Cracked 

Cracked 

Cracked 

Cracked 

387 

20 

25 

Cracked 

Good 

Cracked 

Good 

Cracked 

Good 

288 

lfi 

30 

Good 

Good 

Good 

Cracked 

Good 

Good 

289 

1U 

35 

Cracked 

Cracked 

Cracked 

Good 

Cracked 

Cracked 

Slips  which  cracked  showed  a  tendency  to  curl  up  and 
flake.    All  slips  are  opaque  at  Cone  9. 

SERIES   42. 
(On  Biscuit) 


Constan 

:     N.  C.  Kaolin,   55;   English  Ball, 

10;  Carbonate  of  Soda,   1. 

Cone  5                                     Cone   7 

Cone  9 

Flint 

Spar 

Unglazed    |       Glazed      1     Unglazed    I        Glazed 

Unglazed    |        Glazed 

290 

30 

5 

Cracked 

Good 

Cracked 

Good 

Cracked 

Good 

291 

25 

10 

Cracked 

Good 

Cracked 

Cracked 

Cracked 

Cracked 

292 

20 

15 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

293 

15 

20 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

294 

10 

25 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

295 

5 

30 

Cracked 

Good 

Cracked 

Good 

Cracked 

Good 

This  series  acts  very  similarly  to  Series  41. 

SERIES  42. 
(On  Leather  Hard) 


No 

Cone  5 

Cone  7 

Cone  9 

290 

Good 

Good 

Good 

291 

Good 

Good 

Good 

292 

Good 

Good 

Good 

293 

Good 

Good 

Good 

294 

Good 

Good 

Good 

295 

Good 

Good 

Good 

ON   THE   MANUFACTURE   OF  ENAMEL   BRICK. 


29 


All  slips  are  good  both  glazed  and  unglazed,  except 
that  the  glaze  flakes  from  the  slip  slightly.  Slips,  how- 
ever, fit  perfectly.    All  slips  are  opaque  at  Cone  9. 


SERIES  43. 
(On  Biscuit) 


Constant:     N.  C.  Kaolin,  65;  English  Ball,  10;  Carbonate  of  Soda,  1. 


Cone   5 

Cone  7 

Cone  9 

Flint 

Spar 

Unglazed       |        Glazed 

Unglazed    |        Glazed 

Unglazed      |         Glazed 

296 

20 

5 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

297 

15 

10 

Cracked 

Cracked 

Cracked 

Good 

Cracked 

Cracked 

29S 

10 

15 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

299 

5 

20 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

30f) 

0 

25 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracking  is  very  bad.     Slips  also  flake  some  but  not 
badly.    All  slips  are  opaque  at  Cone  9. 


SERIES  43. 
(On  Leather  Hard) 


No. 

Cone   5 

Cone  7 

Cone  8 

296 

Good 

Good 

Good 

297 

Good 

Good 

Good 

298 

Good 

Good 

Good 

299 

Good 

Good 

Good 

300 

Good 

Good 

Good 

All  slips  work  perfectly  both  glazed  and  unglazed. 
Glaze,  however,  flaked  from  slips;  otherwise  all  trials  were 
sound. 


30 


ON   THE   MANUFACTURE   OP   ENAMEL   BRICK. 


TRANS. AM. CER.SOC.  VOL.XII. 

Groc//iJT. 

MC  Kaolin  *  15-65 
Brandy wine6par~  5-55 
Onto  8/tr.  Hint  -  0-60 

Constants  Not  flotted$) 

Encf.  Ball(riKejNozo)*/0, 
Carbonate  <5oda~  I, 


STULL 


A  =  Good  On  Biscuit 
K=  C^ajeat    " 
C  =  CracKed »    >> 


U^Gooct  On  Lea.t/zer>/iczT>ct       <yft 


Conclusions  on  Group  II, 

The  conclusions  drawn  with  respect  to  crazing-  and 
cracking  in  Group  I  apply  to  Group  II.  There  is  a  ten- 
dency of  slips  high  in  clay  to  flake  as  well  as  crack  on 
biscuit  body.  Series  42  and  43,  which  are  applied  to  leath- 
er hard  body  as  well  as  biscuit,  gave  good  results  on  the 
leather  hard  body,  but  cracked  on  biscuit. 

In  comparing  the  tri-axial  diagram  of  Group  II  with 
that  of  Group  I  it  is  observed  that  the  substitution  of 
Pikes  No.  20  English  ball  clay  for  Tennessee  ball  clay  No. 
1,  has  given  a  much  smaller  field  of  good  slips  on  biscuit 
body;  cracking  has  increased  and  crazing  of  slips  de- 
creased. Good  slips  are  obtained  which  possess  satisfac- 
tory working  qualities  on  leather  hard  body.  None  of  the 
slips  were  good  on  bone  dry  body. 


ON    THE   MANUFACTURE   OP   ENAMEL   BRICK. 


31 


The  limits  of  composition   for  good  slips  on  biscuit 
found  in  this  group  are: 

North    Carolina   Kaolin 15  to  25 

Brandy  wine  Feldspar    15  to  55 

Ohio  Flint    15  to  50 

Pikes  No.  20  Eng.  Eall  Clay 10  )  n       .      . 

Carbonate  of  Soda   1  \  constant 

The  limits  for  good  slips  on  leather  hard  body  are : 

North    Carolina    Kaolin 55  to  65 

Brandywine  Feldspar   5  to  30 

Ohio  Flint    0  to  30 

Pikes  No.  20  Eng.  Ball  Clay 10  I  Pnnctnnt 

Carbonate  of  Soda   1  /  constant 

Group  III — Series  44  to  49. 

SERIES   44. 
(On  Biscuit) 


Constant: 

English  China,  15;  English  Ball 

,  10;  Carbonate  of  Soda,  1. 

Cone  5 

Cone  6 

Cone  8 

No. 

Flint 

par 

Unglazed       |         Glazed 

1     Unglazed      |       Glazed 

Unglazed     |       Glazed 

301 

60 

15 

Cracked 
Crazed 

Crazed 

Cracked 
Crazed 

Crazed 

Cracked 
Crazed 

Crazed 

302 

55 

20 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

303 

50 

25 

Cracked 
Crazed 

Crazed 

Cracked 
Crazed 

Crazed 

Cracked 
Crazed 

Crazed 

301 

45 

30 

Crazed 
Cracked 

Crazed 

Cracked 
Crazed 

Good 

Cracked 
Crazed 

Crazed 

305 

40 

35 

Crazed 

Crazed 

Cracked 

Good 

Crazed 

Good 

306 

35 

40 

Cracked 
Crazed 

Crazed 

Crazed 
Cracked 

Crazed 

Crazed 
Cracked 

Crazed 

307 

30 

45 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

Good 

308 

25 

50 

Crazed 

Crazed 

Cracked 

Good 

Good 

Good 

309 

20 

55 

Crazed 

Crazed 

Crazed 

Good 

Good 

Good 

All  slips  crazed.  Glaze  also  crazed  at  low  tempera- 
tures. Increase  of  temperature  decreases  crazing  of  the 
glaze.  The  glaze  tends  to  present  crazing  of  the  slip.  Very 
little  difference  is  noticed  in  crazing  of  the  slip  due  to 
difference  in  heat  treatment.  A  decrease  in  crazing  is 
noticeable  with  reduction  of  flint  and  increase  in  feldspar. 
Cracking  is  due  to  excessive  fire  shrinkage.  Slips  are  all 
quite  dense. 


32 


ON    THE   MANUFACTURE   OF   ENAMEL   BRICK. 


SERIES   44. 
(On  Bone  Dry) 


No. 

Cone   5 

Cone  6 

Cone  8 

Unglazrd 

I         Glazed 

Unt  lazed 

Glazrd 

1     Unglazed 

Glazed 

301 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

302 

Cracked 

Cracked 

Crazed 

Crazed 

Cracked 

Cracked 

Crazed 

Crazed 

Crazed 

Crazed 

•303 

Cracked 

Cracked 

Cracked 

Crazed 

Cracked 

Cracked 

Crazed 

Crazed 

Crazed 

Cracked 

Crazed 

Crazed 

304 

Cracked 

Cracked 

Cracked 

Crazed 

Cracked 

Cracked 

Crazed 

Crazed 

Crazed 

Cracked 

Crazed 

Crazed 

305 

Cracked 

Cracked 

Cracked 

Crazed 

Cracked 

Cracked 

Crazed 

Crazed 

Crazed 

Cracked 

Crazed 

Crazed 

306 

Crazed 

Cracked 

Cracked 

Crazed 

Cracked 

Cracked 

Cracked 

Crazed 

Crazed 

Cracked 

Crazed 

Crazed 

307 

Crazed 

Cracked 

Crazed 

Crazed 

Cracked 

Cracked 

Cracked 

Crazed 

Cracked 

Crazed 

Crazed 

308 

Crazed 

Cracked 

Cracked 

Crazed 

Cracked 

Cracked 

Cracked 

Crazed 

Crazed 

Cracked 

309 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

Iii  general,  slips  crack  badly.  Cracking  extends 
down  into  body.  Crazing  is  the  same  as  observed  on  bis- 
cuit. Nearly  all  slips  are  vitrified.  Nos.  304  to  309  are 
glossed  in  the  nnglazed  condition  at  Cone  8. 

SERIES   45. 
(On  Biscuit) 


Constant: 

English  China,  25;  English  Ball,  10;  Carbc 

mate  of  Soda,  1. 

Cone  5 

Cone  6 

Cone  8 

Unglazed     |         Glazed 

I     Unglazed 

|         Glazed 

Unglazed      |         Glazfrt 

310 

50 

15 

Crazed 
Cracked 

Good 

Good 

Good 

Good 

Cracked 

311 

45 

20 

Crazed 
Cracked 

Crazed 

Cracked 

Cracked 

Cracked 

Cracked 

31 9, 

40 

25 

Crazed 

Good 

Good 

Good 

Good 

Cracked 

313 

35 

30 

Good 

Good 

Good 

Cracked 

Good 

Cracked 

314 

30 

35 

Cracked 

Good 

Crazed 

Good 

Cracked 

Good 

315 

25 

40 

Cracked 

Good 

Crazed 

Cracked 

Cracked 

Cracked 

316 

20 

415 

Cracked 

Cracked 

Good 

Good 

Cracked 

Cracked 

317 

15 

50 

Good 

Good 

Good 

Good 

Cracked 

Cracked 

Crazing  of  slips  decreases  with  decrease  of  flint  and 


ON    THE   MANUFACTURE   OF   ENAMEL   BRICK. 


33 


increase  of  feldspar.  Crazing  also  increases  with  increase 
in  temperature.  Slips  are  all  opaque  at  Cone  4.  No.  317 
is  translucent  at  Cone  6.  Slips  313  to  317  are  translucent 
at  Cone  8. 

SERIES   45. 
(On  Bone  Dry) 


No. 

Cone  4                                      Cone  6 

Cone  8 

Unglazed    |        Glazed       1     Unglazed     '        Glazed 

Unglazed    |         Glazed 

310 

Cracked 
Crazed 

Cracked 

Cracked 
Crazed 

Good 

Good 

Cracked 

311 

Cracked 

Cracked 

Cracked 
Crazed 

Cracked 

Cracked 

Cracked 

312 

Cracked 

Cracked 

Cracked 
Crazed 

Cracked 

Cracked 

Cracked 

313 

Good 

Cracked 

Cracked 
Crazed 

Cracked 

Cracked 

Cracked 

314 

Cracked 

Cracked   Cracked 

Cracked 

Cracked 

Cracked 

Crazed 

315 

Cracked 

Cracked 

Cracked 
Crazed 

Cracked 

Cracked 

Cracked 

316 

Good 

Cracked 

Cracked 
Crazed 

Cracked 

Cracked 

Cracked 

317 

Cracked 

Cracked 

Cracked 
Crazed 

Cracked 

Cracked 

Cracked 

Slips  behave  in  a  similar  manner  to  what  they  do  on 
biscuit,  except  that  they  crack  worse  and  have  a  slight 
tendency  to  flake. 


SERIES   45. 
(On  Leather  Hard) 


No, 

Cone  4 

Cone  6 

Cone  8 

310 

Flaked 
Crazed 

Flaked 

Flaked 

311 

Flaked 
Crazed 

Flaked 

Good 

312 

Flaked 
Crazed 

Flaked 

Flaked 

313 

Cracked 

Cracked 

Cracked 

314 

Flaked 

Flaked 

Flaked 

315 

Flaked 

Flaked 

Flaked 

316 

Good 

Good 

Good 

317 

Flaked 

Flaked 

Flaked 

34 


ON   THE   MANUFACTURE   OF   ENAMEL   BRICK. 


Both  unglazed  and  glazed  slips  flake  some.     Slip  313, 
which  cracked,  was  dipped  quite  thick. 

SERIES  46. 
(On  Leather  Hard) 


No. 

Constant 

Flint 

Spar 

Cone  3 

Cone  5 

Cone  8 

lOOH 
CO  rH 

318 

45 

10 

Good 

Good 

Good 

319 

'O 

40 

15 

Good 

Good 

Flaked 

320 

w 

35 

20 

Cracked 

Good 

Good 

321 

a    • 

30 

25 

Flaked 

Flaked 

Flaked 

322 

■Sso 

25 

30 

Good 

Good 

Good 

323 

OpQ5 

20 

35 

Flaked 

Good 

Flaked 

324 

English 
English 
Carbona 

15 

40 

Good 

Good 

Good 

325 

10 

45 

Flaked 

Good 

Good 

Slips  have  a  slight  tendency  to  flake.  Flaking  not 
bad.  Some  very  good  slips  appear.  All  are  opaque  at 
Cone  2.  Slips  323  to  325  are  vitrified  at  Cone  6.  Slips 
321  to  325  are  vitrified  at  Cone  8. 

SERIES  47. 
(On  Leather  Hard) 


No 

Constant 

Flint 

Spar 

Cone  4 

Cone  5 

Cone  8 

uioh 

•f    T- 

d 

326 

o 

40 

5 

Good 

Good 

Good 

327 

35 

10 

Good 

Good 

Flaked 

328 

30 

15 

Good 

Good 

Good 

329 

."  —   O 

25 

20 

Cracked 

Cracked 

Flaked 

330 

Offl^ 

20 

25 

Flaked 

Flaked 

Flaked 

331 

.22.2  o 

15 

30 

Flaked 

Flaked 

Flaked 

332 

10 

35 

Good 

Flaked 

Flaked 

bo  fact- 

--■=.- 

HHO 

Slips  flake  more  than  Series  46.  Flaking  seems  to 
increase  with  increase  in  feldspar  and  increase  in  temper- 
ature. All  are  opaque  at  Cone  4.  Slips  330  to  332  are 
translucent  at  Cone  9. 


ON    THE   MANUFACTURE   OF   ENAMEL    BRICK. 


35 


SERIES  48. 
(On  Leather  Hard) 


No. 

Constant 

Flint 

Spar 

Cone  4 

Cone  6 

Cone  8 

333 

to  c 

ua  r- 

tH 

30 

5 

Cracked 

Good 

Cracked 

334 

O 

25 

10 

Good 

Flaked 

Flaked 

335 

c3     • 

£3        *-> 

•S  s  o 

20 

15 

Flaked 

Flaked 

Good 

336 

Opq  © 

15 

20 

Flaked 

Good 

Good 

337 

glish 
glish 
rbona 

10 

25 

Flaked 

Flaked 

Flaked 

338 

5 

30 

Flaked 

Flaked 

Good 

This  series  appears  very  similar  to  Series  47 
opaque  at  Cone  8. 


All  are 


SERIES   49. 
(On  Leather  Hard) 


Flaking  in  this  series  has  increased  over  Series  48. 
All  are  opaque  at  Cone  9. 


36 


ON   THE   MANUFACTURE   OP   ENAMEL   BRICK. 


TRANS.  AM.  CER.  SOC.  VOLXII. 


Group  M. 

M.  O.B.  Encf.  China  Clay  =/5to65 
Brandym'neFelcLs/i.  -5to55, ' 
Ohio  8  Hr.  Flint    -  ot>  60 

Constants  Not  Ftotted    $>. 
E71(].BaU(Pif(e6No.20)*10 

Carbonate  6oda  *  A. 


Clay 
3D 


STULL 


■$ 


A  -   Good  On  Biscuit 
K  ■*   Crazed  »      » 
□  -  GoocfOn  Leather  Hard 


C  =  CracKed  Os  A0* 

F  =  HaKed  On Leather     <k\ 


Hard. 


Conclusions  on  Group  III. 


Grazing  and  Cracking :  The  same  conclusions  on  craz- 
ing found  in  Groups  I  and  II  also  apply  to  Group  III. 
Crazing  of  the  slips  has  increased  considerably  over  the 
two  preceding  groups.  Since  cracking  is  so  erratic,  no 
definite  conclusions  can  be  drawn. 

Flaking :  Flaking  on  leather  hard  trials  during  burn- 
ing appears  to  be  caused  by  too  high  clay  content.  Decreas- 
ing clay  and  increasing  flint  or  feldspar,  or  both,  decreases 
flaking  during  burning.  Increasing  flint  overcomes  flak- 
ing more  effectively  than  increasing  feldspar.  With  clay 
constant,  decrease  of  flint  and  increase  of  feldspar  in- 
creases flaking.  The  trials  also  show  that  flaking  increases 
with  increase  in  burning  temperature. 

The  slips  plotted  as  good  on  biscuit  are  in  reality 


ON    THE   MANUFACTURE   OF   ENAMEL    BRICK. 


37 


doubtful.  This  field  has  dwindled  considerably  when  com- 
pared to  Groups  I  and  II.  A  field  of  good  slips  on  leather 
hard  trials  appears  in  an  entirely  different  locality  on  the 
tri-axial  diagram  than  that  obtained  in  Group  II. 

The  comparison  of  Groups  II  and  III  shows  that  the 
substitution  of  M.  G.  R.  English  China  clay  for  North 
Carolina  kaolin  has  increased  crazing  and  cracking  on 
biscuit  trials,  and  increased  flaking  and  cracking  on 
leather  hard  trials.  Examination  of  the  trials  shows  that 
th<j  English  china  clay  produces  slips  which  approach 
whiteness  more  closely  and  which  vitrify  at  a  lower  tem- 
perature. 

The  limits  of  composition  for  good  slips  on  biscuit 
body  are  doubtful.  None  of  the  slips  were  good  on  bone 
dry  body.  For  leather  hard  body  the  limits  of  composition 
of  good  slips  found  in  this  group  lie  between : 

M.  G.  R.  English  China  Clay 35  to  55 

Brandy  wine  Feldspar    5  to  20 

Ohio  Flint    30  to  45 

Pikes  No.  20  English  Ball  Clay 10  i  n       .      . 

Carbonate  of  Soda   1\  ^onstant 

SERIES  50. 
(On  Biscuit) 


Constant:     Georgia  Kaolin.    15;   Tenn.   Ball,   10;   Carbonate  of   Soda.   1. 

No. 

Eng. 
Flint         C. 
Stone 

Cone  5 

Cone  7                                        Cone  9 

Unelazed     1         Glazed 

Unelazed     1         Glazed      1    Unelazed     I        '.'iaze.1 

344 

60 

15 

Crazed 

Crazed 

Crazed 

Crazed 

Good 

Good 

345 

55 

20 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

346 

50 

25 

Crazed 

Crazed 

Crazed 

Good 

Crazed 

Good 

347 

45 

30 

Crazed 

Good 

Good 

Good 

Good 

Good 

348 

40 

35 

Crazed 

Good 

Crazed 

Good 

Good 

Good 

349 

35 

40 

Good 

Good 

Good 

Good 

Good 

Good 

350 

30 

45 

Crazed 

Good 

Crazed 

Good 

Good 

Good 

351 

25 

50 

Good 

Good 

Good 

Good 

Good 

Good 

Crazing  decreases  with  decrease  in  flint  and  increase 
in  Cornwall  stone.  Crazing  also  decreases  with  increase 
in  temperature.  All  are  opaque  at  Cone  4.  No.  351  is 
translucent  at  Cone  7.     Slips  340  to  351  are  translucent 


38 


ON   THE   MANUFACTURE   OF   ENAMEL   BRICK. 


at  Cone  9.  No.  351  without  glaze  has  a  beautiful  porcelain 
texture  at  cones  7  and  9.  Its  texture  is  a  beautiful  imita- 
tion of  blue  white  marble. 

Group  IV.    Series  51  to  56. 

SERIES   51. 
(On  Biscuit) 

Constant:     N.  C.  Kaolin,  15;  Tenn.  Ball,  10;  Carbonate  of  Soda,  1. 


Eng. 

Cone  G 

Cone  7 

C011€ 

9 

No. 

Flint 

C. 

Stone 

Unglazed 

Glazed 

Unglazed 

Glazed 

Unglazed 

Glazed 

352 

60 

15 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

Good 

353 

55 

20 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

Good 

354 

50 

25 

Crazed 

Crazed 

Crazed 

Good 

Good 

Good 

355 

45 

30 

Crazed 

Good 

Good 

Good 

Good 

Good 

356 

40 

35 

Crazed 

Good 

Crazed 

Good 

Good 

Good 

357 

35 

40 

Good 

Good 

Good 

Good 

Good 

Good 

358 

30 

45 

Crazed 

Good 

Crazed 

Good 

Good 

Good 

359 

25 

50 

Good 

Good 

Good 

Good 

Good 

Good 

Aside  from  crazing,  slips  fit  the  body  very  well.  Craz- 
ing decreases  with  decrease  in  flint,  increase  in  Cornwall 
stone  and  increase  in  temperature.  All  are  opaque  at 
Cone  6.  Slips  357  to  359  are  vitrified  at  Cone  7.  Nos.  355 
to  359  are  vitrified  at  Cone  9.  Slip  No.  359  has  a  beautiful 
parian  marble  texture  at  cones  7  and  9.  Series  not  so 
white  as  Series  50. 

SERIES   52. 
(On  Biscuit) 


Constant: 

N.  C  Kaolin,  25;  Tenn.  Ball,  10;  Carbonate  of  Soda,  1. 

Flint 

Eng. 

c. 

Stone 

Cone  6 

Cone  7                            Cone  9 

Unglazed    1         Glazed 

Unglazed    |         Glazed         i     Unglazed    1     Glazed 

360 

50 

15 

Crazed 

Good 

Good 

Good 

Good 

Good 

361 

45 

20 

Crazed 

Good 

Cracked 

Good 

Cracked 

Good 

362 

40 

25 

Good 

Good 

Good 

Good 

Good 

Good 

363 

35 

30 

Good 

Good 

Good 

Good 

Good 

Good 

364 

30 

35 

Good 

Good 

Cracked 

Good 

Good 

Good 

365 

25 

40 

Good 

Good 

Good 

Good 

Cracked 

Good 

366 

20 

45 

Good 

Good 

Cracked 

Good 

Cracked 

Good 

367 

15 

50 

Good 

Good 

Good 

Good 

Good 

Good 

ON   THE   MANUFACTURE   OF   ENAMEL   BRICK. 


39 


Slips  have  a  slight  tendency  to  crack  as  the  tempera- 
ture of  burning  increases.  All  glazed  slips  were  sound. 
All  are  opaque  at  Cone  6.  Slips  365  to  367  are  vitrified  at 
Cone  7.     Slips  363  to  367  are  vitrified  at  Cone  9. 

SERIES   53. 
(On  Biscuit) 


Constant: 

N.  C.  Kaolin,  35;  Tenn.  Ball,  1C 

;  Carbonate  of  Soda, 

l. 

Eng 

Cone  G 

Cone  7 

Cone  9 

No. 

Flint 

C. 
Stone 

Unglazed      1         Glazed 

Unglazed      I         Glazed 

Unglazed      1     Glazed 

368 

45 

10 

Cracked 

Good 

Cracked 

Good 

Cracked 

Good 

369 

40 

15 

Cracked 

Good 

Cracked 

Good 

Cracked 

Good 

370 

35 

20 

Cracked 

Good 

Cracked 

Cracked 

Cracked 

Good 

371 

30 

25 

Cracked 

Good 

Good 

Good 

Good 

Good 

372 

25 

30 

Cracked 

Good 

Good 

Good 

Good 

Good 

373 

20 

35 

Good 

Good 

Good 

Good 

Cracked 

Good 

374 

15 

40 

Good 

Good 

Good 

Good 

Good 

Good 

375 

10 

45 

Cracked 

Cracked 

Cracked 

Good 

Cracked 

Good 

( 'racking  in  this  series  has  increased  over  that  ob- 
served in  Series  52.  Cracking  has  evidently  increased  with 
increase  in  clay.  Cracking  decreases  with  decrease  in  flint 
and  increase  in  Cornwall  stone,  but  this  is  not  borne  out 
in  all  cases.  Slips  are  all  opaque  at  Cone  6.  Slips  373  to 
375  are  vitrified  at  Cone  7.  Nos.  371  to  375  are  vitrified 
at  Cone  9. 

SERIES   54. 
(On  Biscuit) 


Con 

stant 

N.  C.  Kaolin,  45;  Tenn.  Ball, 

10;  Carbonate  of  Soda 

,  l. 

EDg. 

Cone  G                             Cone  7 

Cone  S 

Flitt 

C. 
Stone 

Unglazed      1         Glazed       1     Unglazed      |         Glazed 

Unglazed      |         Glaze.l 

376 

40 

5 

Cracked 

Good 

Cracked 

Good 

Cracked 

Cracked 

377 

35 

10 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Good 

378 

30 

15 

Cracked 

Good 

Cracked 

Cracked 

Cracked 

Good 

379 

25 

20 

Cracked 

Good 

Cracked 

Good           Cracked 

Good 

380 

20 

25 

Cracked 

Good 

Cracked 

Good 

Cracked 

Cracked 

381 

15 

30 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

382 

10 

35 

Cracked 

Cracked 

Cracked 

Good 

Cracked 

Cracked 

40 


ON    THE    MANUFACTURE   OF   ENAMEL    BRICK. 


Cracking  has  increased.  Glaze  is  not  able  to  prevent 
cracking  though  it  reduces  it.  Slips  are  all  opaque  at 
Cones  6  and  7.     Slip  382  is  translucent  at  Cone  S. 

SERIES   55. 
(On  Biscuit) 


Constant 

:     N.  C.  Kaolin,  55;  Tenn.  Ball, 

1.0;  Carbonate  of  Soda 

1. 

Eng. 

Cone  6 

Cone  7 

Cone  s 

No, 

Flint 

C. 

Stone 

Unglazed    I      Glazed 

Unglazed  |     Glazed 

Unglazed    I     Glazed 

383 

5 

30 

Good 

Cracked 

Good 

Good 

Good 

Cracked 

3S4 

10 

25 

Cracked 

Cracked 

Cracked 

Cracked     Cracked 

Cracked 

385 

15 

20 

Good 

Cracked 

Cracked 

Cracked 

Good 

Cracked 

386 

20 

15 

Cracked 

Cracked 

Good 

Cracked 

Good 

Cracked 

387 

25 

10 

Good 

Cracked 

Cracked 

Cracked 

Good 

Cracked 

388 

30 

5 

Cracked 

Cracked 

Cracked 

Cracked 

Good 

Cracked 

Cracking  has  steadily  increased  with  increase  of 
clay.  Increase  of  temperature  seems  to  increase  cracking. 
All  slips  are  opaque  at  Cone  8. 


SERIES   50. 
(On  Biscuit) 


Constant 

:     N.  C  Kaolin,  65:  T 

enn.  Ball, 

10;  Carbonate  of  Soda 

.  1. 

Eng. 

Cone   3 

Cone  5 

Cone  7 

No. 

Flint 

C. 

Stone 

Unglazed   i     Glazed 

Unglazed   1     Glazed 

Unglazed    1     Glazed 

389 

20 

5 

Cracked 

Crazed 

Crazed 

Good 

Good 

Cracked 

390 

15 

10 

Cracked 

Good 

Cracked 

Cracked 

Cracked 

Good 

391 

10 

15 

Cracked 

Crazed 
Cracked 

Cracked 

Good 

Cracked 

Good 

392 

5 

20 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Good 

393 

0 

25 

Cracked 

Good 

Cracked 

Cracked 

Cracked 

Good 

Slips  are  not  cracked  so  badly  as  in  Series  55,  but 
probably  due  to  the  fact  that  the  slips  in  Series  56  are 
burned  at  correspondingly  lower  temperatures.  Slips  do 
not  craze  but  glaze  shows  crazing  at  Cone  2,  in  fine  zigzag 
lines. 


ON    THE    MANUFACTURE   OF   ENAMEL    BRICK. 


41 


TRANS.  AM.  CER.SOC.  VOL.XIL 

Orou/i  JY. 

N.C.  Kaolin      =f5fo65 
Enq.C.dtone     -  S&50 

0/2 ios/fr  Flint  -  o&eo 

Constants  Atot  Plotted  <$, 

Tenn.BaUAlai  *  w  ' 
Carbonate  6oda=  fy 


■^ .°  A  -  Good  On  Biscuit 

r*  C'CracKed*     ' 


-|— J7//M  ^-/'c/7  Did  Not        0}  (V 
Cra^e  But  Over  W/i  lei?       r  . 
Glaje  Craved-  "-* 


Conclusions  on  Group  IV. 

Crazing'.  Crazing  of  slips  decreases  with  decrease  in 
flint  and  increase  in  clay  or  Cornwall  stone,  or  both.  In- 
creasing- clay  is  more  effective  in  reducing  crazing  than 
increasing  Cornwall  stone.  With  flint  constant,  decreas- 
ing clay  and  increasing  Cornwall  stone  increases  crazing. 
These  observations  are  the  same  as  those  noted  in  the  three 
preceding  groups,  which  shows  the  similar  influences  of 
feldspar  and  Cornwall  stone  upon  crazing  of  slips.  With 
respect  to  the  temperature  of  burning  the  opposite  is  true. 
In  Group  IV,  increasing  burning  temperature  decreases 
crazing. 

Cracking  is  due  to  high  content  of  clay.  Reducing 
clay  and  increasing  flint  or  Cornwall  stone,  or  both,  re- 
duces cracking.     In  one  series  evidence  is  presented  that 


42 


ON    THE    MANUFACTURE   OP   ENAMEL   BRICK. 


increasing  Cornwall  stone  is  more  effective  in  reducing 
cracking  than  increasing  flint,  though  this  is  not  borne 
out  in  all  cases  and  is  opposite  to  what  was  observed  in 
Group  I,  with  respect  to  flint  and  feldspar.  Experience 
in  the  manufacture  of  enamel  brick  shows  that  replace 
ment  of  Cornwall  stone  by  flint  reduces  cracking. 

In  comparing  Groups  I  and  IV  it  is  evident  that  the 
replacement  of  feldspar  by  Cornwall  stone  has  given  a 
smaller  field  of  good  slips  on  biscuit  body,  and  has  reduced 
crazing  and  increased  cracking. 

The  limits  of  composition  of  good  slips  on  biscuit 
hodj  found  in  this  group  are: 

North  Carolina  Kaolin   15  to  35 

English  Cornwall  Stone    15  to  50 

Ohio  Flint    15  to  45 

Tennessee  Ball  Clay  No.  1 10  )  r, 

Carbonate  of  Soda 1  \  <-onstant 

Group  V.    Semes  57  to  62. 

SERIES   57. 
(On  Biscuit) 


Con 

stant 

:     N. 

C.  Kaolin, 

15;  English  Ball  No 

1,  10;  Carbonate  of 

Soda,  1. 

Eng. 

Cone   3 

Co 

ne  5 

Cone  S 

No. 

Flint 

C. 

Stone 

1  Unglazed  1     Glazed 

Unglazed  |     Glazed 

Unglazed 

Glazed 

394 

60 

15 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

395 

55 

20 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

Good 

396 

50 

25 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

Good 

397 

45 

30 

Crazed 

Good 

Crazed 

Crazed 

Good 

Good 

398 

40 

35 

Crazed 

Crazed 

Crazed 

Good 

Crazed 

Good 

399 

35 

40 

Crazed 

Good 

Good 

Good 

Good 

Good 

400 

30 

45 

Crazed 

Good 

Crazed 

Good 

Good 

Good 

401 

25 

50 

Good 

Good 

Crazed 

Good 

Good 

Good 

402 

20 

55 

Good 

Good 

Crazed 

Good 

Good 

Good 

Slips  craze  quite  badly.  Glaze  tends  to  prevent  craz- 
ing of  slips.  Crazing  decreases  with  decrease  in  flint,  in- 
creases in  Cornwall  stone  and  increase  in  temperature.  All 
are  opaque  at  Cone  4.  Nos.  401  and  402  are  vitrified  at 
Cone  6.     Slips  309  to  402  vitrified  at  Cone  8. 


ON    THE   MANUFACTURE   OF   ENAMEL   BRICK. 


43 


SERIES   57. 
(On  Bone  Dry) 


No. 

Cone  3 

Coi 

ie  5 

Cone  8 

Unglazed 

Glazed 

Unglazed 

Glazed 

Un  glazed 

Glazed 

394 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

395 

Crazed 

Crazed 

Crazed 

Good 

Crazed 

Good 

396 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

Good 

397 

Crazed 

Good 

Crazed 

Good 

Crazed 

Good 

398 

Crazed 

Good 

Crazed 

Good 

Cracked 

Cracked 

399 

Good 

Good 

Good 

Good 

Good 

Good 

400 

Good 

Good 

Good 

Good 

Good 

Good 

401 

Cracked 

Good 

Cracked 

Good 

Cracked 

Cracked 

402 

Cracked 

Good 

Cracked 

Cracked 

Cracked 

Cracked 

Cracking  is 


Slips  fit  quite  well.     Crazing  is  practically  the  same 
as  that  observed  in  the  same  slips  on  biscuit, 
slight. 

SERIES  58. 
(On  Biscuit) 


Constant:     N.  C.  Kaolin,   25;   English   Ball,   10;   Carbonate  of  Soda,   1. 

Enj, 

C. 

Stone 

Cone  4                          Cone  0 

Cone  8 

Unglazed  I     Glazed     Unglazed  |     Glazed 

Unglazed   1      Glazed 

403 

50 

15 

Good 

Good 

Good 

Good 

Good 

Good 

404 

45 

20 

Good 

Good 

Good 

Good 

Good 

Good 

405 

40 

25 

Good 

Good 

Good 

Good 

Good 

Good 

406 

35 

30 

Good 

Cracked 

Cracked 

Good 

Good 

Good 

407 

30 

35 

Cracked 

Cracked 

Good 

Good 

Good 

Good 

408 

25 

40 

Good 

Good 

Good 

Good 

Good 

Cracked 

409 

20 

45 

Good 

Good 

Good 

Good 

Good 

Good 

410 

15 

50 

Good 

Good 

Good 

Good 

Good 

Good 

Slips  have  slight  tendency  to  crack  when  applied  too 
thick,  otherwise  they  seem  to  fit  perfectly.  All  are  opaque 
at  Cone  6.    Slips  407  to  -110  are  vitrified  at  Cone  8. 


44  ON    THE   MANUFACTURE   OF   ENAMEL   BRICK. 

SERIES   58. 
(On  Bone  Dry) 


No. 

Cone  4 

Cone  g 

Cone  S 

Unglazed 

Glazed 

Unglazed    1 

Glazed 

Unglazed 

Glazed 

403 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

404 

Good 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

405 

Good 

Good 

Cracked 

Cracked 

Cracked 

Good 

406 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

407 

Good 

Good 

Cracked 

Cracked 

Cracked 

Good 

408 

Cracked 

Cracked 

Cracked 

Good 

Good 

Good 

409 

Cracked 

Cracked 

Cracked 

Cracked 

Good 

Cracked 

410 

Cracked 

Cracked 

Cracked 

Cracked 

Good 

Cracked 

Slips  crack  slightly  in  line  lines.  Some  are  very  good. 
These  slips  would  probably  work  well  for  spraying  on 
bone  dry  bodv. 


SERIES   59. 
(On  Biscuit) 


Coi 

stant 

:      N. 

C.   Kaolin, 

33;   English   Ball   No 

20,   10;   Carbonate  of 

Soda.   1. 

No       Flint 

Eng, 

C. 

Stone 

Cone  2 

Cone  7                                Cone  S 

Unglazed   |     Glazed 

Unglazed   1     Glazed     ;    Unglazed  |      Glazed 

411 

45 

10 

Good 

Cracked 

Cracked 

Cracked 

Good 

Cracked 

412 

40 

15 

Good 

Good           Good 

Cracked 

Good 

Good 

413 

35 

20 

Cracked 

Cracked     Cracked 

Cracked 

Cracked 

Cracked 

414 

30 

25 

Cracked 

Cracked     Good 

Cracked 

Cracked 

Cracked 

415 

25 

30 

Good 

Cracked  j  Cracked 

Cracked 

Cracked 

Cracked 

416 

20 

35 

Good 

Cracked     Cracked 

Cracked 

Cracked 

Cracked 

417 

15 

40 

Good 

Cracked  j  Cracked 

Cracked 

Good 

Cracked 

418 

10 

45 

Good 

Good           Good 

Good 

Good 

Good 

Cracking  has  increased  more  than  in  Series  58.  Crack- 
ing evidently  increases  with  increase  in  clay.  Replace- 
ment of  flint  by  Cornwall  stone  does  not  seem  to  influence 
crack  i  112;. 


ON    TTIE    MANUFACTURE   OF   EXA1IEL    URICK. 


45 


SERTE3   59. 
(On  Bone  Dry) 


Cone  3 


Dnglazed    |      Glazed 


Cone  7 


Cone  S 


Dnglazed    i      Glazed      ;,  Dnglazed    I      Glassed 


411 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

412 

Good 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

413 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

414 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

415 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

416 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

417 

Cracked 

Cracked 

Good 

Cracked 

Cracked 

Cracked 

418 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracking  has  increased  markedly  over  Series  58  on 
1m me  dry.     As  a  rule  the  glaze  reduces  cracking. 

SERIES   60. 
(On  Biscuit) 


Constant 

:  N. 

C.  Kaolin, 

45:  English.  Fall  No. 

20,  10;  Ca 

rbonate  of 

Soda.  1. 

No. 

Flint 

Spar. 

Cone  3 

Cone  7 

Cone  8 

Dnglazed 

Glazed 

Dnglazed 

1  Glazed 

Dnglazed 

Glazed 

419 

35 

10 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

420 

30 

15 

Good 

Cracked 

Good 

Cracked 

Cracked 

Cracked 

421 

25 

20 

Good 

Cracked 

Good 

Cracked 

Good 

Cracked 

422 

20 

25 

Good 

Cracked 

Good 

Cracked 

Good 

Cracked 

423 

15 

30 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

424 

10 

65 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Slips  crack  badly.  Difference  in  composition  and  heat 
treatment  do  not  seem  to  influence  the  degree  of  cracking. 


SERIES   61. 
(On  Biscuit) 


<"<  nstant:     N.    C.   Kaolin,   55;   English  Ball   No.   20,   10;   Carbonate  of   Soda,   1. 


Erg. 

cone  5 

Cone  7 

Cone  8 

No. 

Flint 

C. 

ctonr 

Dnglazed  |   Glazed 

Dnglazed  |   Glazed 

Dnglazed  1   Glazed 

425 

30 

5 

Cracked 

Cracked 

Good 

Cracked 

Good 

Cracked 

426 

25 

10 

Cracked 

Cracked 

Cracked 

Cracked 

Good 

Cracked 

427 

20 

15 

Cracked 

Cracked 

Cracked 

Cracked 

Good 

Cracked 

428 

15 

20 

Good 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

429 

10 

25 

Good 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

430 

5 

30 

Good 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

46 


ON    THE    MANUFACTURE   OF   ENAMEL   BRICK. 


Slips  crack  and  curl  up  a  little.     Cracking  seems  to 
increase  by  replacement  of  flint  by  Cornwall  stone. 


SERIES   61. 
(On  Leather  Hard) 


Cone   5 

Cone   7 

Cone  8 

Unglazed 

Glazed 

Unglazed 

|      Glazed 

Unglazed 

Glazed 

425 

Good 

Good 

Good 

Good 

Good 

Cracked 

426 

Good 

Good 

Good 

Flaked 

Good 

Cracked 

427 

Good 

Good 

Good 

Good 

Good 

Cracked 

428 

Good 

Good 

Good 

Flaked 

Cracked 

Cracked 

429 

Flaked 

Cracked 

Flaked 

Flaked 

Cracked 

Cracked 

430 

Good 

Flaked 

Good 

Flaked 

Cracked 

Cracked 

Slips  were  applied  a  little  too  thick.  Some  flaking 
occurs  but  not  bad.  Glaze  flakes  loose  from  slips  in  a  few 
cases. 

SERIES   62. 
(On  Biscuit) 

Constant:     N.  C.  Kaolin,  65;  English  Ball  No.  20,  10;  Carbonate  of  Soda,   1. 


Eng. 

C.  ne   5                                            Ct.ne  7 

Cone  8 

No. 

Flint 

C. 

Stf.ne 

Unglazed   |     Glazed     1  Unglazed    |     Glazed 

Unglazed    1      Glazed 

431 

20 

5 

Good 

Cracked 

Good 

Cracked 

Good 

Cracked 

432 

15 

10 

Good 

Cracked 

Good 

Cracked 

Good 

Cracked 

433 

10 

15 

Cracked 

Cracked 

Cracked 

Cracked 

Good 

Cracked 

434 

5 

20 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

435 

0 

25 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Series  62  on  biscuit:     This  series  cracks  worse  than 
any  other  series  in  the  group.    Slips  curl- up  some. 

SERIES   62. 
(On  Leather  Hard) 


No. 

Cone  5                                  Cone  7 

Cone  S 

Unglazed    1      Glazed      1  Unglazed    |       Glazed 

Unglazed    |      Glazed 

431 
432 
433 
434 
435 

Good 

Flaked 

Flaked 

Good 

Good 

Flaked 

Good 

Flaked 

Flaked 

Flaked 

Flaked 

Flaked 

Good 

Good 

Good 

Flaked 
Flaked 
Flaked 
Flaked 
Flaked 

Flaked 

Flaked 

Flaked 

Cracked 

Good 

Flaked 
Flaked 
Flaked 
Flaked 
Good 

Slips  flake  some.     Glaze  also  flakes  a  little.     Slip  No. 
435.  however,  is  very  good  at  Cone  8. 


OX   THE   MANUFACTURE   OF   ENAMEL    BRICK. 

TRAN5.  AM.CER.50C.  VOLXII. 


47 


Claif 
90J 


G?*ou/7  V. 

N.  C.  Kaolin  =  J5tb  65 
Ena.C.iStone  =  6  to  55 
Ohio  Stir.  Flint*  ototo 

Constants  Not  Plotted  1^; 

Eng.  Ball  (PiKesNo.2o)*tL 
Carbonate  dooia  ^  I 


A     Good  On  Biscuit 

Q       »       '  Leatner/tard 

q       *        »  Bone  Dry 


K,  Craved  On  B/sca/t 

C    Crac/Ced »       -■> 

p  FlaKed  On  Leather  /iard  ^ 


crs- 


Conclusions  on  Group  V. 

Grazing  and  Cracking:  The  observations  on  crazing 
nnd  cracking  in  Group  V  are  the  same  as  those  of  Group 
IV. 

Flaking:  Flaking  on  leather  hard  hotly  during  burn- 
ing increases  with  increase  in  clay.  Reducing  clay  and 
increasing  flint  or  Cornwall  stone,  or  both,  reduces  flaking 
during  burning.  The  opposite  is  true  of  flaking  in  dip- 
ping. 

Comparing  Groups  A  and  IV  shows  a  decrease  in 
number  of  good  slips  on  biscuit  body  by  substituting  Pikes 
Xo.  20  English  ball  clay  for  Tennessee  No.  1  ball  clay. 
Cracking  and  crazing  hare  increased.  (See  comparison  of 
Groups  I  and  II.) 

In  comparing  Groups  V  and  II  it  is  shown  that  the 


48 


ON   THE   MANUFACTURE   OP   ENAMEL   BRICK. 


substitution  of  Cornwall  stone  for  feldspar  has  increased 
crazing  and  flaking.  Cracking  remains  practically  the 
same.  The  fields  of  good  slips  on  biscuit  and  leather  hard 
bodies  are  smaller.  A  few  good  slips  on  bone  dry  body 
appear  in  Group  V  which  are  lacking  in  Group  II. 

The   limits   of   composition   of   good   slips   found   in 
Group  V  are : 


On    Biscuit 


On  Bone   Dry 


On  Leather  Hard 


North  Carolina  Kaolin 

English  Cornwall   Stone. . . 

Ohio  Flint    

Carbonate   of   Soda 

Pikes  No.  20  English  Ball. 


15   to   25 

15   to   55 

15   to   50 

10 

1 


15    to   25 
25   to   45 

to   40 

10 
1 


25 


55   to  65 

5   to  25 

0   to  30 

10 


Constant 


Group  VI.    Series  63  to  68. 

SERIES  63. 
(On  Biscuit) 


Constant 

English  China 

,  15;  English  Ball  No 

20,   10;  Carbonate  of 

Soda,  1. 

Flint 

En? 
C. 

Stone 

Cone  3 

Cone  6 

Cone  8 

Unglazed 

I     Glazed 

Unglazed 

I      Glazed 

Unglazed 

Glazed 

436 

60 

15 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

437 

55 

20 

Good 

Crazed 

Good 

Crazed 

Good 

Crazed 

438 

50 

25 

Crazed 

Crazed 

Good 

Crazed 

Good 

Good 

439 

45 

30 

Good 

Crazed 

Good 

Crazed 

Good 

Good 

440 

40 

35 

Crazed 

Crazed 

Good 

Good 

Good 

Good 

441 

35 

40 

Good 

Crazed 

Good 

Good 

Good 

Good 

442 

30 

45 

Good 

Crazed 

Good 

Good 

Good 

Good 

443 

25 

50 

Good 

Crazed 

Good 

Good 

Good 

Good 

444 

20 

55 

Good 

Good 

Good 

Good 

Good 

Good 

Slips  high  in  flint  craze.  Glaze  tends  to  prevent  craz- 
ing of  slips.  Crazing  decreases  with  decrease  in  flint,  in- 
crease in  Cornwall  stone  and  increase  in  temperature.  All 
slips  are  opaque  at  Cone  3.  Slips  43S  to  444  are  vitrified 
at  Cone  9. 


ON    THE   MANUFACTURE   OF   ENAMEL   BRICK. 


49 


SERIES   63. 


(On  Bone  Dry) 


No. 

Cone  3 

Cone  6 

Con< 

s 

Unglazed 

1      Glazed 

Unglazed 

Glazed 

Unglazed 

Glazed 

436 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

437 

Crazed 

Crazed 

Crazed 

Crazed 

Crazed 

Good 

438 

Good 

Crazed 

Good 

Good 

Good 

Good 

439 

Good 

Crazed 

Good 

Crazed 

Good 

Good 

440 

Good 

Crazed 

Good 

Crazed 

Good 

Good 

441 

Good 

Crazed 

Good 

Good 

Good 

Good 

442 

Good 

Crazed 

Good 

Good 

Good 

Cracked 

443 

Good 

Good 

Cracked 

Cracked 

Cracked 

444 

Good 

Good 

Good 

Good 

Crazed 

Good 

Crazing  of  slips  practically  the  same  as  that  observed 
in  the  same  series  on  biscuit.  Slips  fit  body  very  good, 
though  not  perfectly. 

SERIES   64. 
(On  Biscuit) 


Constant:     English  China,   25;  English  Ball  No.  20,  10;  Carbonate  of  Soda,  1. 


Ene. 

Coie  3 

Cone  6 

Cone  8 

\o. 

Flint 

c. 

Stone 

Unglazed 

I     Glazed 

Unglazed 

Glazed 

Unglazed 

Glazed 

445 

50 

15 

Good 

Crazed 

Good 

Crazed 

Good 

Crazed 

446 

45 

20 

Good 

Crazed 

Good 

Crazed 

Good 

Crazed 

447 

40 

25 

Good 

Crazed 

Good 

Crazed 

Good 

Good 

448 

35 

30 

Good 

Good 

Good 

Good 

Good 

Good 

449 

30 

35 

Good 

Good 

Good 

Good 

Good 

Good 

450 

25 

40 

Good 

Good 

Good 

Good 

Good 

Good 

451 

20 

45 

Good 

Good 

Good 

Good 

Good 

Good 

452 

15 

50 

Good 

Good 

Good 

Good 

Good 

Good 

Slips  fit  body  perfectly  aside  from  crazing.  Crazing 
decreases  with  decrease  in  flint*  and  increase  in  Cornwall 
stone.  All  are  opaque  at  Cone  2.  Slips  448  to  452  are 
vitrified  at  Cone  6.  Slips  446  to  452  are  vitrified  at 
Cone  7. 


50  OX    THE    MANUFACTUBE   OF   ENAMEL   BRICK, 

SERIES   64. 
(On  Bone  Dry) 


Cone  2 

Cone  6 

Cone  7 

Unglazed 

Glazed 

Unglazed 

Glazed    i 

Unglazed 

Glazed 

445 

Good 

Crazed 

Good 

Crazed 

Cracked 

Crazed 

446 

Cracked 

Cracked 

Cracked 

Crazed 

Cracked 

Crazed 

447 

Cracked 

Crazed 

Cracked 

Crazed 

Cracked 

Good 

448 

Cracked 

Crazed 

Cracked 

Good 

Cracked 

Cracked 

449 

Crazed 

Crazed 

Cracked 

Cracked 

Cracked 

Cracked 

450 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

Cracked 

451 

Cracked 

Good 

Good 

Good 

Good 

Good 

452 

Good 

Cracked 

Cracked 

Good 

Cracked 

Good 

The  cracking,  which  is  of-  the  so-called  "crowsfoot" 
type,  is  not  bad.  Variation  in  composition  and  tempera- 
ture do  not  seem  to  influence  the  degree  of  cracking.  No. 
451  is  very  good  at  Cones  6  and  7. 


SERIES   64. 


(On  Leather  Hard) 


No. 

Cone  2 

Cone  6 

Cone  7 

Unglazed    ,      Glazed 

Unglazed    |       Glazed 

Unglazed    1        Glazed 

445 
446 
447 
448 
449 
450 
451 
452 

Flaked 

Good 

Good 

Good 

Good 

Good 

Good 

Good 

Flaked 

Flaked 

Good 

Good 

Good 

Good 

Good 

Good 

Flaked 

Good 

Good 

Good 

Good 

Good 

Good 

Good 

Flaked      j  Flaked 
Flaked     !  Good 
Good           Good 
Good           Good 
Good           Flaked 
Flaked        Good 
Good           Good 
Good           Good 

Flaked 

Flaked 

Flaked 

Flaked 

Flaked 

Flaked 

Good 

Good 

Flaking  appears  to  decrease  with  decrease  of  flint  and 
increase  in  Cornwall  stone.  Glaze  tends  to  reduce  the 
degree  of  flaking,  but  not  to  overcome  it.  A  subsequent 
examination  of  duplicate  .trials  showed  that  slips  were 
imperfectly  bonded  before  burning  since  slips  could  be 
flaked  off  in  small  patches  by  pressing  with  the  thumb 
nail. 


ON    THE   MANUFACTURE   OF   ENAMEL   BRICK. 

SERIES   65. 

(On  Leather  Hard) 


51 


Constant:     English  China,  35;  English  Ball  No.  20,  10;  Carbonate  of  Soda,  1. 

No. 

Flint 

Ene-   1                    Cone  4 

Cone  6 

Cone  7 

Stone  1      I'.iglazed       I         Glazed 

Unglazed      |         Glazed 

Unglazed      1       Glazed 

453 

45 

10 

454 

40 

15 

455 

35 

20 

456 

30 

25 

457 

25 

30 

458 

20 

35 

459 

15 

40 

460 

10 

45 

Good 
Good 
Good 
Good 
Good 
Good 
Good 
Good 


Good 

Flaked 

Flaked 

Good 

Good 

Good 

Good 

Good 


Good 

Flaked 

Good 

Good 

Good 

Good 

Good 

Good 


Flaked 

Flaked 

Flaked 

Good 

Good 

Good 

Good 

Good 


Good 
Good 
Good 
Good 
Good 
Good 
Good 
Good 


Flaked 

Good 

Flaked 

Good 

Good 

Good 

Good 

Good 


Flaking  is  less  than  in  Series  64.  Flaking  decreases 
with  decrease  in  flint  and  increase  in  Cornwall  stone. 
Slips  456  to  466  are  good  hard  slips  at  Cone  7.  No.  460 
is  a  dense  white  porcelain. 


SERIES   66. 
(On  Leather  Hard) 


Constant:     English  China,  45;   English  Ball  No.   20,   10;  Carbonate  of  Soda,  1. 

No. 

Flint 

Eng. 

c. 

Stone 

Cone  2 

Cone  6 

Cone  7 

Unglazed    |     Glazed 

Unglazed    1     Glazed 

Unglazed    1     Glazed 

461 

40 

5 

Good 

Good 

Good 

Good 

Good 

Good 

462 

35 

10 

Good 

Good 

Good 

Good 

Good 

Good 

463 

30 

15 

Good 

Flaked 

Flaked 

Flaked 

Good 

Flaked 

464 

25 

20 

Good 

Good 

Good 

Good 

Good 

Good 

465 

20 

25 

Good 

Good 

Good 

Good 

Good 

Good 

466 

15 

30 

Good 

Good 

Good 

Good 

Good 

Good 

467 

10 

35 

Good 

Good 

Good 

Good 

Good 

Good 

Slips  fit  body  very  well.  Slip  No.  463  is  the  only  one 
that  showed  any  signs  of  flaking.  Glaze  has  a  tendency  to 
flake  on  the  slips.  Slips  464  to  467  are  excellent  as  to  fit, 
color  and  hardness. 


52  ON   THE   MANUFACTURE   OF   ENAMEL    BRICK. 

SERIES   67. 
(On  Leather  Hard) 


Constant:     English  China,  55;  English  Ball  No.  20,  10;  Carbonate  of  Soda,  1. 

No 

Flint 

Ene. 

c. 

Stone 

Cone  4 

Cone  6 

Cone  7 

Unelazed     I        Glazed 

Unglazed     |        Glazed 

Unglazed      |         Glazed 

468 

30 

5 

469 

25 

10 

470 

20 

15 

471 

15 

20 

472 

10 

25 

473 

5 

30 

Good 
Good 
Good 
Good 
Good 
Good 


Good 
Good 
Good 
Good 
Good 
Good 


Good 
Good 
Good 
Good 
Good 
Good 


Good 
Good 
Good 
Good 
Good 
Good 


Good 
Good 
Good 
Good 
Good 
Good 


Good 
Good 
Good 
Good 
Good 
Good 


All  slips  fit  body  perfectly.  No  cracking-  0r  flaking 
could  be  detected.  This  is  the  best  series  in  the  group. 
Slips  470  to  473  are  especially  good  at  Cones  6  and  7. 

SERIES   68. 
(On  Leather  Hard) 


Constant: 

English  China,  65;  E 

nglish  Ball 

,  10;  Carbonate  of  Soda,  1. 

Eng. 

Cone  4 

Cone  7 

No. 

Flint 

C. 
Stone 

Unglazed 

Glazed 

Unglazed 

Glazed 

Unglazed     |        Glazed 

474 

20 

5 

Good 

Good 

Flaked 

Flaked 

Flaked 

Flaked 

475 

15 

lu 

Good 

Flaked 

Flaked 

Flaked 

Flaked 

Flaked 

476 

10 

15 

Good 

Good 

Good 

Good 

Good 

Good 

477 

5 

20 

Good 

Good 

Good 

Good 

Good 

Good 

478 

0 

25 

Good 

Good 

Good 

Good 

Good 

Good 

Slips  high  in  clay  and  flint  have  a  tendency  to  flake. 
Decrease  of  flint  and  increase  of  Cornwall  stone  has  re- 
Slips  477  and  478  are  very  good. 


duced  flaking. 


ON    THE   MANUFACTURE   OF   ENAMEL   BRICK. 


53 


TRANS.  AM  CER.  SOC.  VOL.  XII 

6 roup  W. 

M.  G.  ft.  Eng.  China~/5to  65 
Eng.  C.  Stone         *  Sto55 
0/iio8Hr.riint       ~0to60, 

Con  jfants  A'ot  Piotted $L 

Eng.  BaU(fi/<esMzo)*  /O 
Carbonatedoda^J  ' 


STULL 


A=  Good On  Biscuit 

□  *       »        »   /.eattierh/ar>d 

K  -  Crazed.  On  Btecui't 


O   Good  On  Bo?ieff?y        0}  A? 
F   FiaXed  On  Leat/te/Wa  rd  rJ 


Conclusions  on  Group  VI. 

Crazing :  Practically  the  same  conclusions  on  crazing 
of  the  slip  apply  in  this  group  as  those  observed  in  Groups 
IV  and  V. 

Cracking:  Very  little  cracking  occurred  in  slips  ap- 
plied to  bone  dry  body.  Xo  cracking  occurred  in  slips 
applied  to  biscuit  and  leather  hard  bodies. 

Flaking:  Slips  both  low  and  high  in  clay  showed  a 
tendency  to  flake.  Evidently  slips  low  in  clay  were  im- 
perfectly bonded  before  burning.  Flaking  decreases  with 
decrease  in  flint  and  increase  in  Cornwall  stone. 

A  comparison  of  Groups  VI  and  V  shows  that  the 
substitution  of  M.  G.  E.  English  China  clay  for  North 
Carolina  kaolin  has  decreased  crazing,  cracking  and  flak- 
ing.    The  fields  of  good  slips  on  biscuit  body  are  practi- 


54 


ON    THE   MANUFACTURE   OF   ENAMEL    BRICK. 


cally  the  same  size.  A  larger  number  of  good  slips  appear 
on  bone  dry  body,  and  the  field  of  good  slips  on  leather 
hard  body  has  expanded  to  a  comparatively  large  area. 
The  slips  are  also  superior  in  whiteness  and  vitrify  at 
lower  temperatures. 

A  comparison  of  Groups  VI  and  ITT  shows  that  the 
substitution  of  English  Cornwall  stone  for  feldspar  has 
decreased  crazing,  cracking  and  flaking.  The  fields  of 
good  slips  on  biscuit  and  leather  hard  bodies  have  in- 
creased and  good  slips  on  bone  dry  were  obtained,  which 
are  absent  in  Series  III. 

The  limits  of  composition  of  good  slips  found  in 
Group  VI  are : 


Or 

Biscuit 

On  Lcathe 

Hard 

On 

Bone  Dry 

M.  G. 

R.  English  China  Clay. 

15 

to 

25 

25 

to 

65 

15 

to 

25 

English    Cornwall    Stone 

25 

to 

55 

0 

to 

50 

25 

to 

55 

Ohio 

Flint    . 

15 

to 

50 

0 

to 

45 

20 

to 

50 

Pikes 

No.  20 

Eng.  Ball  Clay. 

10 

10 

10 

Carbonate  of 

1 

1 

1 

GENERAL  DEDUCTIONS. 

From  previous  practical  experience  in  the  manufac- 
ture of  enamel  brick  and  from  the  foregoing  investiga- 
tions, the  following  rules  are  given  for  overcoming  defects 
in  enamel  brick  slips : 


ON    THE   MANUFACTURE    OF   ENAMEL   BRICK. 


55 


Defects  Arising  in  the  Application  of  the   Slips   and 
Remedies  for  the  Same. 


Principal 
Defects 


1. 

Using  freshly  made  slips. 

1. 

Age     slips     a     week     or 

Pinholes 

more. 

2. 

Dust   on   the    surface   of 
brick. 

2. 

Remove  all  dust  or  scrub 
the  surfaces  to  be  dip- 
ped. 

3 

Pinholes   in   the   surface 
of  the  brick. 

3. 

Scrub  surfaces  to  be 
dipped. 

4. 

Bad   dipping. 

4. 

5. 

(See  Fig.  1,  p.  717.) 

5. 

Too  high  content  of  clay 

Reduce  clay  and  increase 

in  slip. 

the  non-plastic  portion, 
or  add  a  soluble  mater- 
ial as  carbonate  of  soda, 
borax  or  silicate  of  soda. 

Cracking 

6. 

Slips   too   high  in   China 
clay  or  kaolin. 

6. 

Decrease  China  clay  or 
kaolin  and  increase  ball 
clay,  or  add  a  soluble 
material. 

7. 

Allowing     leather     hard 
body  to  get  too  dry  be- 

7. 

Dip  brick  in  a  softer 
condition. 

fore   dipping. 

8. 

Do   not    apply    slip    over 

8. 

Applying   slip   too   thick. 

J  r>  of  an  inch  thick. 

9. 

Too  fine  grinding  of  slip. 

9. 

Blunge  slips  instead  of 
grinding. 

Flakim 


10.  Using    slips    too    low    in    10. 
clay. 

11.  Slips   too   high  in   China   11. 
clay  or  kaolin. 

12.  Oil    or    dust    on    dipping   12. 
surface. 

13.  In     dipping     on     leather    13. 
hard ;     dipping    before 
brick  have  hardened  suf- 
ficiently. 


increase  clay  and  de- 
crease non-plastic  por- 
tion. 

Decrease  China  clay  or 
kaolin  and  increase  ball 
clay. 

Scrub  surfaces  to  be 
dipped. 

Allow  brick  to  reach  a 
firm  leather  hard  condi- 
tion before  dipping. 


56 


ON    THE   MANUFACTURE   OF   ENAMEL   BRICKS. 


Slip  Defects  Arising  in  Burning  and  Remedies  for  the 

Same. 


Principal 
Defects 


14. 

Slips  too  high  in  flint. 

14. 

Reduce  flint  and  in- 
crease clay,  feldspar  or 
Cornwall  stone. 

15. 

Slips    too    high    in    feld- 
spar  or   Cornwall   stone. 

15. 

Reduce  feldspar  or  Corn 
wall  stone  and  increase 
clay. 

Crazing 

16. 

With  feldspar  as  a  flux; 
burning  slips  at  too  high 
a  temperature. 

16. 

Reduce  burning  temper- 
ature. 

17. 

With   Cornwall   stone  as 
a   flux;    burning   slips   at 

17. 

Increase  burning  tem- 
perature. 

18. 

too  low  a  temperature. 
Too  high  content  of  clay 

18. 

Reduce      clay     and      in- 

in slips. 

crease  flint,  Cornwall 
stone   or   feldspar. 

Cracking 

19. 

Too  high  content  of  feld- 
spar   or    Cornwall    stone 
in  slips. 

19. 

Reduce  feldspar  or  Corn- 
wall stone  and  increase 
flint. 

20. 

Dipping    slips   too    thick. 

20. 

Same  as  No.  8. 

21. 

Too  high  content  of  clay 
in  slips. 

21. 

Reduce  clay  and  in- 
crease Cornwall  stone, 
flint    or  feldspar. 

22. 

Too  high  content  of  feld- 
spar in  slips. 

22. 

Reduce  feldspar  and  in- 
crease  Cornwall   stone. 

Flaking 

23. 

Too  high  content  of  flint 
in  slips. 

23. 

Reduce  flint  and  in- 
crease   Cornwall    stone. 

24. 

Burning  slips  at  too  high 

24. 

Reduce    burning   temper- 

a  temperature. 

ature. 

SLIPS  TESTED  AS  ENGOBES  FOR  STONEWARE. 

The  problem  of  producing  a  slip  or  engobe  to  be  used 
as  a  white  lining  for  stoneware  was  confronted.  Slips  No. 
292,  298,  464  and  470  were  selected  as  the  starting  point. 
These  slips  were  applied  to  three  different  stoneware  clays, 
viz. :  Whitehall  clay  from  Whitehall,  111.,  having  a  com- 
paratively high  shrinkage:  Macomb  clay  of  medium 
shrinkage  from  Macomb,  111. ;  Bloomingdale  clay  having  a 
comparatively  low  shrinkage  from  Bloomingdale,  Ind. 

Trials  were  made  in  the  form  of  cups,  jiggered  in  one 
piece.     Cnps  were  taken  from  the  molds,  finished  leather 


ON   THE    MANUFACTURE   OF   KXA1IEL   BRICK. 


57 


hard,  and  slips  applied  to  the  inside  in  two  coats.  Over 
this  a  clear  glaze  was  applied  in  one  coat.  The  slip  and 
glaze  were  scraped  off  at  the  outside  rim.  A  brown  glaze 
was  applied  to  the  outside  by  sinking  the  cup  down  into 


(Stoneivar'e  Cc//r  W(t/?  lV/}ite£/;$obe 
A 'net  CLeay*  Glaze  /n^side 
/) 'nd  Brown  6/aze  Oot^s  ide. 


the  glaze  until  the  brown  glaze  touched  the  white  slip  and 
glaze  extending  over  the  rim.  The  cups  were  dried  and 
burned  at  Tone  3.  All  four  slips  worked  perfectly  on  all 
three  stoneware  bodies. 

DISCUSSION. 

Mr.  Ramsay.  There  is  a  lot  I  would  like  to  say  on 
this  subject,  as  it  is  an  interesting  one,  but  the  trouble 
we  have  in  the  enamel  brick  business  is  not  with  the  slips 
but  in  the  cost  of  manufacture  and  results  out  of  kilns. 

I  know  Mr.  Stall  has  put  a  good  deal  of  time  and  work 
on  his  paper,  and  I  agree  with  him  on  many  of  his  results. 
To  ^et  a  slip  as  near  to  the  clays  as  possible  you  have  to 
use  lime,  and  when  that  is  added  it  changes  the  results 
entirely.  He  made  the  claim  that  the  slip  will  peal  off 
with  the  dry  clay.     I  would  like  to  take  exception  to  the 


58  ON   THE   MANUFACTURE   OP  ENAMEL   BRICK. 

remark  for  the  reason  that  ball  clay  will  not  come  off. 
With  China  clay  it  will  come  off,  but  by  a  mixture  of  both 
it  will  not  come  off. 

Mr.  Stall :  I  do  not  think  Mr.  Kamsay's  statement  is 
antagonistic  to  what  has  been  brought  out  in  my  paper. 
If  a  slip  is  high  enough  in  ball  clay  it  will  cling  to  the 
body.  Enamel  brick  makers  as  well  as  potters  are  limited 
in  the  amount  of  ball  clay  they  can  use  on  account  of  the 
bad  color  it  imparts.  For  this  reason  1  used  ten  per  cent 
ball  clay  as  the  high  limit  in  all  slips. 

It  is  quite  essential  to  have  some  ball  clay  in  the  slip, 
but  as  a  rule  the  less  ball  clay  present  the  better  color  you 
get.  My  experience  shows  that  a  slip  made  from  ball  chvy 
will  stick  very  well  but  will  crack  badly.  Ball  clay 
possesses  better  adhesive  qualities  than  China  clay  or  kao- 
lin, and  seems  to  adjust  itself  better  to  the  body  both  in 
drying  and  burning. 

Mr.  Ashley:  I  think  to  slightly  increase  the  China 
clay  slip  by  adding  a  small  quantity  of  silicate  of  soda, 
will  give  some  of  the  general  characteristics  of  ball  clay. 

Mr.  Ramsay:  It  may  be  in  certain  respects.  If  yon 
add  a  certain  percentage  of  silicate  of  soda  you  destroy 
the  working  qualities  as  regards  the  dipping.  I  suppose 
the  idea  is  to  decrease  the  water  content  and  that  only 
affects  the  drying  shrinkage.  There  is  no  effect  afterwards, 
of  course,  and  I  think  the  difference  is  so  slight  that  it  is 
hardly  worth  trying. 

Mr.  Stull :  My  experience  in  using  silicate  of  soda 
was  that  it  caused  the  slip  to  settle  very  rapidly  and  cake 
hard  at  the  bottom.  It  requires  constant  agitation  to 
keep  the  slip  in  suspension.  Perhaps  I  was  using  too  high 
a  percentage,  although  it  was  only  %  of  one  per  cent,  how- 
ever. 

Mr.  Ashley-.  I  would  suggest  that  even  1/10  of  one 
per  cent  of  silicate  of  soda  acts  very  vigorously  on  clay, 
and  we  should  experiment  with  1/100  of  one  per  cent 
rather  than  1/10. 


OX    THE    MANUFACTURE   OP   ENAMEL    BRICK.  59 

Mr.  Worcester:  I  would  like  to  ask  Mr.  Stull  if  he 
lias  studied  the  hardness  of  these  slips  with  the  various 
contents  of  spar.  In  some  work  we  have  been  doing  at 
Ohio  State  that  was  one  of  the  requirements  to  produce  a 
hard  or  nearly  steel  hard  slip  and  I,  of  course,  am  very 
much  interested,  and  was  wondering  if  Mr.  Stull  had  ob- 
served this  point  in  particular  or  at  all. 

Mr.  Stull :  When  each  slip  was  shaken  up  and  turned 
out  of  the  can  before  dipping,  a  little  of  it  was  cast  into 
trials,  1%"  long,  y2"  wide  and  14"  thick.  These  were 
placed  in  the  sagger  and  burned  with  the  dipped  trials  and 
used  to  determine  the  porosity.  It  was  desirable  to  know 
what  was  the  limit  of  porosity  for  these  slips  which  would 
withstand  the  freezing  test.  That  part  of  the  work  is 
under  way  at  the  present  time. 

Mr.  Stover:  I  would  like  to  ask  what  percentage  of 
absorption  you  got,  or  was  it  around  1%?  You  spoke  of 
making  trials  for  absorption  for  your  slips  and  that  would 
follow  in  your  paper.  I  happen  to  be  looking  along  that 
iine  just  now  and  would  like  to  know. 

Mr.  Stull:  There  are  two  methods  of  determining  the 
porous  nature  of  brick.  One  is  the  percentage  of  absorp- 
tion and  one  is  the  percentage  of  porosity.  The  absorption, 
as  Ave  know,  is  usually  determined  by  weighing  the  brick 
dry  then  soaking  it  48  hours  and  weighing  it  again.  By 
observing  the  increase  in  weight  and  dividing  that  increase 
by  the  weight  of  the  brick  gives  what  is  called  percentage 
absorption.  The  percentage  porosity  is  approximately  2^0 
times  percentage  absorption.  The  porosity  of  these  slips 
was  determined  by  Prof.  Purdy's  formula.  The  porosities 
of  the  slips  have  varied  according  to  the  kind  and  amount 
of  flux  and  the  temperature  of  burning.  Perfect  fitting 
slips  Avere  obtained  from  as  soft  as  chalk  up  to  a  hard 
vitrified  and  glossed  condition. 

Mr.  Stover:  And  do  you  not  remember  in  figures 
what  the  result  was? 

Mr.  Stull :     Xo,  I  do  not. 


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